7 RDF Semantic Graph Support for Apache Jena

7.1.1 If You Used a Previous Version of the Support for Apache Jena

If you used a previous version of the support for Apache Jena, note the following important changes for this version:

• com.hp.hpl.jena.sparql.core.DataSourceImpl is replaced by com.hp.hpl.jena.sparql.core.DatasetImpl.

  If you have import com.hp.hpl.jena.sparql.core.DataSourceImpl in your Java source code, you will need to update it to import com.hp.hpl.jena.sparql.core.DatasetImpl.

  If you have DataSourceImpl.wrap in your Java source code, you will need to update it to DatasetImpl.wrap".

• joseki-config.ttl is moved under the WEB-INF/classes directory of joseki.war. This configuration file was formerly placed under the top-level directory of joseki.war. The following example shows the new placement:

  % /usr/local/packages/jdk16/bin/jar tf joseki.war
  application.xml
  index.html
  joseki-config-ttl_now_under_WEB-INF_classes
  META-INF/
  META-INF/MANIFEST.MF
  ojdbc6.jar
  StyleSheets/
  StyleSheets/joseki.css
  update.html
  WEB-INF/
  WEB-INF/web.xml
  WEB-INF/lib/
  WEB-INF/lib/httpclient-4.1.2.jar
  WEB-INF/lib/commons-codec-1.5.jar
  WEB-INF/lib/joseki-3.4.4.oracle_fix.jar
  WEB-INF/lib/servlet-api-2.5-20081211.jar
  WEB-INF/lib/xercesImpl-2.10.0.jar
  WEB-INF/lib/sdordf.jar
  WEB-INF/lib/sdordfclient.jar
  WEB-INF/lib/xml-apis-1.4.01.jar
  WEB-INF/lib/slf4j-log4j12-1.6.4.jar
  WEB-INF/lib/slf4j-api-1.6.4.jar
  WEB-INF/lib/jena-tdb-0.9.2.jar
  WEB-INF/lib/log4j-1.2.16.jar
  WEB-INF/lib/jena-arq-2.9.2.jar
  WEB-INF/lib/jena-core-2.7.2.jar
  WEB-INF/lib/jena-iri-0.9.2.jar
  WEB-INF/lib/httpcore-4.1.3.jar
  WEB-INF/classes/
  WEB-INF/classes/joseki-config.ttl
  xml-to-html.xsl
  

7.2.1 Creating the Required Data Source Using WebLogic Server

If you need help creating the required J2EE data source using the WebLogic Server admin console, you can follow these steps:

1. Login to: http://<hostname>:7001/console

2. In the Domain Structure panel, click Services.

3. Click JDBC

4. Click Data Sources.

5. In the Summary of JDBC Data Sources panel, click New under the Data Sources table.

6. In the Create a New JDBC Data Source panel, enter or select the following values.

   Name: OracleSemDS

   JNDI Name: OracleSemDS

   Database Type: Oracle

   Database Driver: Oracle's Driver (Thin) Versions: 9.0.1,9.2.0,10,11

7. Click Next twice.

8. In the Connection Properties panel, enter the appropriate values for the Database Name, Host Name, Port, Database User Name (schema that contains semantic data), Password fields.

9. Click Next.

10. Select (check) the target server or servers to which you want to deploy this OracleSemDS data source.

11. Click Finish.

    You should see a message that all changes have been activated and no restart is necessary.

7.2.2 Configuring the SPARQL Service

By default, the SPARQL Service endpoint assumes that the queries are to be executed against a semantic model with a pre-set name. This semantic model is owned by the schema specified in the J2EE data source with a default JNDI name OracleSemDS. Note that you do not need to create this model explicitly using PL/SQL or Java; if the model does not exist in the network, it will be automatically created, along with the necessary application table and index.

To change the default JNDI name or to use a default semantic model, you can configure the SPARQL service by editing the joseki-config.ttl configuration file, which is embedded under the WEB-INF/classes directory in the prebuilt application joseki_web_app/joseki.war. (If you used a previous version of the support for Apache Jena, note that joseki-config.ttl is now placed under the WEB-INF/classes directory instead of under the top level directory of the web application.)

The supplied joseki-config.ttl file includes a section similar to the following for the Oracle data set:

#
## Datasets
#
[] ja:loadClass "oracle.spatial.rdf.client.jena.assembler.OracleAssemblerVocab" .
 
oracle:Dataset  rdfs:subClassOf  ja:RDFDataset .
 
<#oracle> rdf:type oracle:Dataset;
    joseki:poolSize     1 ;         ## Number of concurrent connections allowed to this dataset.
    oracle:connection
    [ a oracle:OracleConnection ;
      oracle:dataSourceName "OracleSemDS"
    ];
    oracle:defaultModel [ oracle:firstModel "TEST_MODEL" ] .

In this section of the file, you can:

• Modify the joseki:poolSize value, which specifies the number of concurrent connections allowed to this Oracle data set (<#oracle> rdf:type oracle:Dataset;), which points to various RDF models in the database.

• Customize the name of the data source. The default name of OracleSemDS can be changed depending on your application requirements. The name, however, must match the data source name specified in Section 7.2.1, "Creating the Required Data Source Using WebLogic Server".

• Modify the name (or the object value of oracle:firstModel predicate) of the defaultModel, to use a different semantic model for queries. You can also specify multiple models, and one or more rulebases for this defaultModel.

  For example, the following specifies two models (named ABOX and TBOX) and an OWLPRIME rulebase for the default model. Note that models specified using the oracle:modelName predicate must exist; they will not be created automatically.

  <#oracle> rdf:type oracle:Dataset;
      joseki:poolSize 1 ; ## Number of concurrent connections allowed to this dataset.
      oracle:connection
      [ a oracle:OracleConnection ;
        oracle:dataSourceName "OracleSemDS"
      ];
      oracle:defaultModel [ oracle:firstModel "ABOX";
                                        oracle:modelName "TBOX";
                                        oracle:rulebaseName "OWLPRIME" ] .
  

• Specify named graphs in the dataset. For example, you can create a named graph called <http://G1> based on two Oracle models and an entailment, as follows.

  <#oracle> rdf:type oracle:Dataset;
      joseki:poolSize 1 ; ## Number of concurrent connections allowed to this dataset.
        oracle:connection
        [ a oracle:OracleConnection ;
        ];
        oracle:namedModel [ oracle:firstModel "ABOX";
                            oracle:modelName "TBOX";
                            oracle:rulebaseName "OWLPRIME";
                            oracle:namedModelURI <http://G1> ]  .
  

  The object of namedModel can take the same specifications as defaultModel, so virtual models are supported here as well (see also the next item).

• Use a virtual model for queries by adding oracle:useVM "TRUE", as shown in the following example. Note that if the specified virtual model does not exist, it will automatically be created on demand.

  <#oracle> rdf:type oracle:Dataset;
      joseki:poolSize 1 ; ## Number of concurrent connections allowed to this dataset.
      oracle:connection
      [ a oracle:OracleConnection ;
      ];
      oracle:defaultModel [ oracle:firstModel "ABOX";
                                       oracle:modelName "TBOX";
                                       oracle:rulebaseName "OWLPRIME";
                                       oracle:useVM "TRUE"
      ] .
  

  For more information, see Section 7.11.1, "Virtual Models Support".

• Specify a virtual model as the default model to answer SPARQL queries by using the predicate oracle:virtualModelName, as shown in the following example with a virtual model named TRIPLE_DATA_VM_0:

  oracle:defaultModel [ oracle:virtualModelName "TRIPLE_DATA_VM_0" ] .
  

  If the underlying data consists of quads, you can use oracle:virtualModelName with oracle:allGraphs. The presence of oracle:allGraphs causes an instantiation of DatasetGraphOracleSem objects to answer named graph queries. An example is as follows:

  oracle:allGraphs [ oracle:virtualModelName "QUAD_DATA_VM_0" ] .
  

  Note that when a virtual model name is specified as the default graph, the endpoint can serve only query requests; SPARQL Update operations are not supported.

• Set the queryOptions and inferenceMaintenance properties to change the query behavior and inference update mode. (See the Javadoc for information about QueryOptions and InferenceMaintenanceMode.)

  By default, QueryOptions.ALLOW_QUERY_INVALID_AND_DUP and InferenceMaintenanceMode.NO_UPDATE are set, for maximum query flexibility and efficiency.

-Doracle.spatial.rdf.client.jena.clientIdentifier=<identificationString>

SQL> EXECUTE DBMS_MONITOR.CLIENT_ID_TRACE_ENABLE('JenaAdapter', true, true);

CREATE TABLE .... (... column definitions ...) ... compress;

-Doracle.spatial.rdf.client.jena.advancedCompression="compress for oltp"

7.2.3 Terminating Long-Running SPARQL Queries

Because some applications need to be able to terminate long-running SPARQL queries, an abort framework has been introduced with RDF Semantic Graph support for Apache Jena and the Joseki setup. Basically, for queries that may take a long time to run, you must stamp each with a unique query ID (qid) value.

For example, the following SPARQL query selects out the subject of all triples. A query ID (qid) is set so that this query can be terminated upon request.

PREFIX ORACLE_SEM_FS_NS:  <http://example.com/semtech#qid=8761>
SELECT ?subject WHERE {?subject ?property ?object }

The qid attribute value is of long integer type. You can choose a value for the qid for a particular query based on your own application needs.

To terminate a SPARQL query that has been submitted with a qid value, applications can send an abort request to a servlet in the following format and specify a matching QID value

http://<hostname>:7001/joseki/querymgt?abortqid=8761

7.2.4 N-Triples Encoding for Non-ASCII Characters

For any non-ASCII characters in the lexical representation of RDF resources, \uHHHH N-Triples encoding is used when the characters are inserted into the Oracle database. (For details about N-Triples encoding, see http://www.w3.org/TR/rdf-testcases/#ntrip_grammar.) Encoding of the constant resources in a SPARQL query is handled in a similar fashion.

Using \uHHHH N-Triples encoding enables support for international characters, such as a mix of Norwegian and Swedish characters, in the Oracle database even if a supported Unicode character set is not being used.

7.6.1 Compilation of SPARQL queries to a single SEM_MATCH Call

SPARQL queries involving DISTINCT, OPTIONAL, FILTER, UNION, ORDER BY, and LIMIT are converted to a single Oracle SEM_MATCH table function. If a query cannot be converted directly to SEM_MATCH because it uses SPARQL features not supported by SEM_MATCH (for example, CONSTRUCT), the support for Apache Jena employs a hybrid approach and tries to execute the largest portion of the query using a single SEM_MATCH function while executing the rest using the Jena ARQ query engine.

For example, the following SPARQL query is directly translated to a single SEM_MATCH table function:

PREFIX dc:  <http://purl.org/dc/elements/1.1/> 
PREFIX rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> 
PREFIX foaf: <http://xmlns.com/foaf/0.1/> 
SELECT ?person ?name 
  WHERE {
                 {?alice foaf:knows ?person . }
               UNION { 
                 ?person ?p ?name. OPTIONAL { ?person ?x ?name1 } 
                     }
        }

However, the following example query is not directly translatable to a single SEM_MATCH table function because of the CONSTRUCT keyword:

PREFIX vcard: <http://www.w3.org/2001/vcard-rdf/3.0#> 
CONSTRUCT  { <http://example.org/person#Alice> vcard:FN ?obj } 
  WHERE  { { ?x <http://pred/a> ?obj.}
         UNION
         { ?x <http://pred/b> ?obj.}  }

In this case, the support for Apache Jena converts the inner UNION query into a single SEM_MATCH table function, and then passes on the result set to the Jena ARQ query engine for further evaluation.

7.6.2 Optimized Handling of Property Paths

As defined in Jena, a property path is a possible route through an RDF graph between two graph nodes. Property paths are an extension of SPARQL and are more expressive than basic graph pattern queries, because regular expressions can be used over properties for pattern matching RDF graphs. For more information about property paths, see the documentation for the Jena ARQ query engine.

RDF Semantic Graph support for Apache Jena supports all Jena property path types through the integration with the Jena ARQ query engine, but it converts some common path types directly to native SQL hierarchical queries (not based on SEM_MATCH) to improve performance. The following types of property paths are directly converted to SQL by the support for Apache Jena when dealing with triple data:

• Predicate alternatives: (p1 | p2 | … | pn) where pi is a property URI

• Predicate sequences: (p1 / p2 / … / pn) where pi is a property URI

• Reverse paths : ( ^ p ) where p is a predicate URI

• Complex paths: p+, p*, p{0, n} where p could be an alternative, sequence, reverse path, or property URI

Path expressions that cannot be captured in this grammar are not translated directly to SQL by the support for Apache Jena, and they are answered using the Jena query engine.

The following example contains a code snippet using a property path expression with path sequences:

String m = "PROP_PATH";
 
ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, m);
 
GraphOracleSem graph = new GraphOracleSem(oracle, m);    
    
// populate the RDF Graph
    graph.add(Triple.create(Node.createURI("http://a"),
    Node.createURI("http://p1"),
    Node.createURI("http://b")));
 
graph.add(Triple.create(Node.createURI("http://b"),
 Node.createURI("http://p2"),
 Node.createURI("http://c")));
 
graph.add(Triple.create(Node.createURI("http://c"),
 Node.createURI("http://p5"),
 Node.createURI("http://d")));
 
String query =
" SELECT ?s  " +
" WHERE {?s (<http://p1>/<http://p2>/<http://p5>)+ <http://d>.}";
   
QueryExecution qexec = 
      QueryExecutionFactory.create(QueryFactory.create(query, 
 Syntax.syntaxARQ), model);
 
try {
  ResultSet results = qexec.execSelect();
  ResultSetFormatter.out(System.out, results);
}
finally {
  if (qexec != null)
    qexec.close();
}
     
OracleUtils.dropSemanticModel(oracle, m);
model.close();

7.7.1 SQL Hints

SQL hints can be passed to a SEM_MATCH query including a line in the following form:

PREFIX ORACLE_SEM_HT_NS: <http://oracle.com/semtech#hint>

Where hint can be any hint supported by SEM_MATCH. For example:

PREFIX ORACLE_SEM_HT_NS: <http://oracle.com/semtech#leading(t0,t1)> 
SELECT ?book ?title ?isbn     
WHERE { ?book <http://title> ?title. ?book <http://ISBN> ?isbn }

In this example, t0,t1 refers to the first and second patterns in the query.

Note the slight difference in specifying hints when compared to SEM_MATCH. Due to restrictions of namespace value syntax, a comma (,) must be used to separate t0 and t1 (or other hint components) instead of a space.

For more information about using SQL hints, see Section 1.6, "Using the SEM_MATCH Table Function to Query Semantic Data", specifically the material about the HINT0 keyword in the options attribute.

7.7.2 Using Bind Variables in SPARQL Queries

In Oracle Database, using bind variables can reduce query parsing time and increase query efficiency and concurrency. Bind variable support in SPARQL queries is provided through namespace pragma specifications similar to ORACLE_SEM_FS_NS.

Consider a case where an application runs two SPARQL queries, where the second (Query 2) depends on the partial or complete results of the first (Query 1). Some approaches that do not involve bind variables include:

• Iterating through results of Query 1 and generating a set of queries. (However, this approach requires as many queries as the number of results of Query 1.)

• Constructing a SPARQL filter expression based on results of Query 1.

• Treating Query 1 as a subquery.

Another approach in this case is to use bind variables, as in the following sample scenario:

Query 1:
 
  SELECT ?x
    WHERE { ... <some complex query> ... };
 
 
Query 2:
 
  SELECT ?subject ?x
    WHERE {?subject <urn:related> ?x .};

The following example shows Query 2 with the syntax for using bind variables with the support for Apache Jena:

PREFIX ORACLE_SEM_FS_NS: <http://oracle.com/semtech#no_fall_back,s2s>
PREFIX ORACLE_SEM_UEAP_NS: <http://oracle.com/semtech#x$RDFVID%20in(?,?,?)>
PREFIX ORACLE_SEM_UEPJ_NS: <http://oracle.com/semtech#x$RDFVID>
PREFIX ORACLE_SEM_UEBV_NS: <http://oracle.com/semtech#1,2,3>
SELECT ?subject ?x
WHERE {
  ?subject <urn:related>  ?x
};

This syntax includes using the following namespaces:

• ORACLE_SEM_UEAP_NS is like ORACLE_SEM_AP_NS, but the value portion of ORACLE_SEM_UEAP_NS is URL Encoded. Before the value portion is used, it must be URL decoded, and then it will be treated as an additional predicate to the SPARQL query.

  In this example, after URL decoding, the value portion (following the # character) of this ORACLE_SEM_UEAP_NS prefix becomes "x$RDFVID in(?,?,?)". The three question marks imply a binding to three values coming from Query 1.

• ORACLE_SEM_UEPJ_NS specifies the additional projections involved. In this case, because ORACLE_SEM_UEAP_NS references the x$RDFVID column, which does not appear in the SELECT clause of the query, it must be specified. Multiple projections are separated by commas.

• ORACLE_SEM_UEBV_NS specifies the list of bind values that are URL encoded first, and then concatenated and delimited by commas.

Conceptually, the preceding example query is equivalent to the following non-SPARQL syntax query, in which 1, 2, and 3 are treated as bind values:

SELECT ?subject ?x
  WHERE {
    ?subject <urn:related>  ?x
  }
  AND ?x$RDFVID in (1,2,3);

In the preceding SPARQL example of Query 2, the three integers 1, 2, and 3 come from Query 1. You can use the oext:build-uri-for-id function to generate such internal integer IDs for RDF resources. The following example gets the internal integer IDs from Query 1:

PREFIX oext: <http://oracle.com/semtech/jena-adaptor/ext/function#>
SELECT ?x  (oext:build-uri-for-id(?x) as ?xid)
WHERE { ... <some complex query> ... };

The values of ?xid have the form of <rdfvid:integer-value>. The application can strip out the angle brackets and the "rdfvid:" strings to get the integer values and pass them to Query 2.

Consider another case, with a single query structure but potentially many different constants. For example, the following SPARQL query finds the hobby for each user who has a hobby and who logs in to an application. Obviously, different users will provide different <uri> values to this SPARQL query, because users of the application are represented using different URIs.

SELECT ?hobby
  WHERE { <uri> <urn:hasHobby> ?hobby };

One approach, which would not use bind variables, is to generate a different SPARQL query for each different <uri> value. For example, user Jane Doe might trigger the execution of the following SPARQL query:

SELECT ?hobby WHERE {
<http://www.example.com/Jane_Doe> <urn:hasHobby> ?hobby };

However, another approach is to use bind variables, as in the following example specifying user Jane Doe:

PREFIX ORACLE_SEM_FS_NS: <http://oracle.com/semtech#no_fall_back,s2s>
PREFIX ORACLE_SEM_UEAP_NS: <http://oracle.com/semtech#subject$RDFVID%20in(ORACLE_ORARDF_RES2VID(?))>
PREFIX ORACLE_SEM_UEPJ_NS: <http://oracle.com/semtech#subject$RDFVID>
PREFIX ORACLE_SEM_UEBV_NS: <http://oracle.com/semtech#http%3a%2f%2fwww.example.com%2fJohn_Doe>
SELECT ?subject ?hobby
  WHERE {
    ?subject <urn:hasHobby>  ?hobby
  };

Conceptually, the preceding example query is equivalent to the following non-SPARQL syntax query, in which http://www.example.com/Jane_Doe is treated as a bind variable:

SELECT ?subject ?hobby
WHERE {
  ?subject <urn:hasHobby>  ?hobby
}
AND ?subject$RDFVID in (ORACLE_ORARDF_RES2VID('http://www.example.com/Jane_Doe'));

In this example, ORACLE_ORARDF_RES2VID is a function that translates URIs and literals into their internal integer ID representation. This function is created automatically when the support for Apache Jena is used to connect to an Oracle database.

7.7.3 Additional WHERE Clause Predicates

The SEM_MATCH filter attribute can specify additional selection criteria as a string in the form of a WHERE clause without the WHERE keyword. Additional WHERE clause predicates can be passed to a SEM_MATCH query including a line in the following form:

PREFIX ORACLE_SEM_AP_NS: <http://oracle.com/semtech#pred>

Where pred reflects the WHERE clause content to be appended to the query. For example:

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX ORACLE_SEM_AP_NS:<http://www.oracle.com/semtech#label$RDFLANG='fr'>  
SELECT DISTINCT ?inst ?label
  WHERE { ?inst a <http://someCLass>. ?inst rdfs:label ?label . }
  ORDER BY (?label) LIMIT 20

In this example, a restriction is added to the query that the language type of the label variable must be 'fr'.

7.7.4 Additional Query Options

Additional query options can be passed to a SEM_MATCH query including a line in the following form:

PREFIX ORACLE_SEM_FS_NS: <http://oracle.com/semtech#option>

Where option reflects a query option (or multiple query options delimited by commas) to be appended to the query. For example:

PREFIX ORACLE_SEM_FS_NS:   
<http://oracle.com/semtech#timeout=3,dop=4,INF_ONLY,ORDERED,ALLOW_DUP=T>
SELECT * WHERE {?subject ?property ?object }

The following query options are supported:

• ALLOW_DUP=t chooses a faster way to query multiple semantic models, although duplicate results may occur.

• BEST_EFFORT_QUERY=t, when used with the TIMEOUT=n option, returns all matches found in n seconds for the SPARQL query.

• DEGREE=n specifies, at the statement level, the degree of parallelism (n) for the query. With multi-core or multi-CPU processors, experimenting with different DOP values (such as 4 or 8) may improve performance.

  Contrast DEGREE with DOP, which specifies parallelism at the session level. DEGREE is recommended over DOP for use with the support for Apache Jena, because DEGREE involves less processing overhead.

• DOP=n specifies, at the session level, the degree of parallelism (n) for the query. With multi-core or multi-CPU processors, experimenting with different DOP values (such as 4 or 8) may improve performance.

• INF_ONLY causes only the inferred model to be queried.

• JENA_EXECUTOR disables the compilation of SPARQL queries to SEM_MATCH (or native SQL); instead, the Jena native query executor will be used.

• JOIN=n specifies how results from a SPARQL SERVICE call to a federated query can be joined with other parts of the query. For information about federated queries and the JOIN option, see Section 7.7.4.1.

• NO_FALL_BACK causes the underlying query execution engine not to fall back on the Jena execution mechanism if a SQL exception occurs.

• ODS=n specifies, at the statement level, the level of dynamic sampling. (For an explanation of dynamic sampling, see the section about estimating statistics with dynamic sampling in Oracle Database SQL Tuning Guide.) Valid values for n are 1 through 10. For example, you could try ODS=3 for complex queries.

• ORDERED is translated to a LEADING SQL hint for the query triple pattern joins, while performing the necessary RDF_VALUE$ joins last.

• PLAIN_SQL_OPT=F disables the native compilation of queries directly to SQL.

• QID=n specifies a query ID number; this feature can be used to cancel the query if it is not responding.

• RESULT_CACHE uses the Oracle RESULT_CACHE directive for the query.

• REWRITE=F disables ODCI_Table_Rewrite for the SEM_MATCH table function.

• S2S (SPARQL to pure SQL) causes the underlying SEM_MATCH-based query or queries generated based on the SPARQL query to be further converted into SQL queries without using the SEM_MATCH table function. The resulting SQL queries are executed by the Oracle cost-based optimizer, and the results are processed by the support for Apache Jena before being passed on to the client. For more information about the S2S option, including benefits and usage information, see Section 7.7.4.2.

  S2S is enabled by default for all SPARQL queries. If you want to disable S2S, set the following JVM system property:

  -Doracle.spatial.rdf.client.jena.defaultS2S=false
  

• SKIP_CLOB=T causes CLOB values not to be returned for the query.

• STRICT_DEFAULT=F allows the default graph to include triples in named graphs. (By default, STRICT_DEFAULT=T restricts the default graph to unnamed triples when no data set information is specified.)

• TIMEOUT=n (query timeout) specifies the number of seconds (n) that the query will run until it is terminated. The underlying SQL generated from a SPARQL query can return many matches and can use features like subqueries and assignments, all of which can take considerable time. The TIMEOUT and BEST_EFFORT_QUERY=t options can be used to prevent what you consider excessive processing time for the query.

SELECT ?s ?s1 ?o
 WHERE { ?s1 ?p1 ?s .
                    {
                     SERVICE <http://sparql.org/books> { ?s ?p ?o }
                    }
                 }

PREFIX ORACLE_SEM_FS_NS:   <http://oracle.com/semtech#join=2>
SELECT ?s ?s1 ?o
 WHERE { ?s1 ?p1 ?s .
                    {
                     SERVICE <http://sparql.org/books> { ?s ?p ?o }
                    }
                 }

PREFIX ORACLE_SEM_FS_NS:   <http://oracle.com/semtech#join=3>
SELECT ?s ?s1 ?o
 WHERE { ?s1 ?p1 ?s .
                    {
                     SERVICE <http://sparql.org/books> { ?s ?p ?o }
                    }
                  }

PREFIX ORACLE_SEM_FS_NS:   <http://oracle.com/semtech#join=1>
SELECT ?s ?s1 ?o
 WHERE { ?s1 ?p1 ?s .
                    {
                     SERVICE <http://sparql.org/books> { ?s ?p ?o }
                    }
                }

-Doracle.spatial.rdf.client.jena.queryCacheSize=<size>

7.7.5 Midtier Resource Caching

When semantic data is stored, all of the resource values are hashed into IDs, which are stored in the triples table. The mappings from value IDs to full resource values are stored in the MDSYS.RDF_VALUE$ table. At query time, for each selected variable, Oracle Database must perform a join with the RDF_VALUE$ table to retrieve the resource.

However, to reduce the number of joins, you can use the midtier cache option, which causes an in-memory cache on the middle tier to be used for storing mappings between value IDs and resource values. To use this feature, include the following PREFIX pragma in the SPARQL query:

PREFIX ORACLE_SEM_FS_NS: <http://oracle.com/semtech#midtier_cache>

To control the maximum size (in bytes) of the in-memory cache, use the oracle.spatial.rdf.client.jena.cacheMaxSize system property. The default cache maximum size is 1GB.

Midtier resource caching is most effective for queries using ORDER BY or DISTINCT (or both) constructs, or queries with multiple projection variables. Midtier cache can be combined with the other options specified in Section 7.7.4.

If you want to pre-populate the cache with all of the resources in a model, use the GraphOracleSem.populateCache or DatasetGraphOracleSem.populateCache method. Both methods take a parameter specifying the number of threads used to build the internal midtier cache. Running either method in parallel can significantly increase the cache building performance on a machine with multiple CPUs (cores).

7.8.1 Functions in the ARQ Function Library

SPARQL queries through the support for Apache Jena can use functions in the function library of the Jena ARQ query engine. These queries are executed in the middle tier.

The following examples use the upper-case and namespace functions. In these examples, the prefix fn is <http://www.w3.org/2005/xpath-functions#> and the prefix afn is <http://jena.hpl.hp.com/ARQ/function#>.

PREFIX  fn: <http://www.w3.org/2005/xpath-functions#>
PREFIX  afn: <http://jena.hpl.hp.com/ARQ/function#>
SELECT (fn:upper-case(?object) as ?object1)
WHERE { ?subject dc:title ?object }

PREFIX  fn: <http://www.w3.org/2005/xpath-functions#>
PREFIX  afn: <http://jena.hpl.hp.com/ARQ/function#>
SELECT ?subject (afn:namespace(?object) as ?object1)
WHERE { ?subject <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?object } 

7.8.2 Native Oracle Database Functions for Projected Variables

SPARQL queries through the support for Apache Jena can use native Oracle Database functions for projected variables. These queries and the functions are executed inside the database. Note that the functions described in this section should not be used together with ARQ functions (described in Section 7.8.1).

This section lists the supported native functions and provides some examples. In the examples, the prefix oext is <http://oracle.com/semtech/jena-adaptor/ext/function#>.

• oext:upper-literal converts literal values (except for long literals) to uppercase. For example:

  PREFIX  oext: <http://oracle.com/semtech/jena-adaptor/ext/function#>
  SELECT (oext:upper-literal(?object) as ?object1)
  WHERE { ?subject dc:title ?object }
  

• oext:lower-literal converts literal values (except for long literals) to lowercase. For example:

  PREFIX  oext: <http://oracle.com/semtech/jena-adaptor/ext/function#>
  SELECT (oext:lower-literal(?object) as ?object1)
  WHERE { ?subject dc:title ?object }
  

• oext:build-uri-for-id converts the value ID of a URI, bNode, or literal into a URI form. For example:

  PREFIX  oext: <http://oracle.com/semtech/jena-adaptor/ext/function#>
  SELECT (oext:build-uri-for-id(?object) as ?object1)
  WHERE { ?subject dc:title ?object }
  

  An example of the output might be: <rdfvid:1716368199350136353>

  One use of this function is to allow Java applications to maintain in memory a mapping of those value IDs to the lexical form of URIs, bNodes, or literals. The MDSYS.RDF_VALUE$ table provides such a mapping in Oracle Database.

  For a given variable ?var, if only oext:build-uri-for-id(?var) is projected, the query performance is likely to be faster because fewer internal table join operations are needed to answer the query.

• oext:literal-strlen returns the length of literal values (except for long literals). For example:

  PREFIX  oext: <http://oracle.com/semtech/jena-adaptor/ext/function#>
  SELECT (oext:literal-strlen(?object) as ?objlen)
  WHERE { ?subject dc:title ?object }
  

7.8.3 User-Defined Functions

SPARQL queries through the support for Apache Jena can use user-defined functions that are stored in the database.

In the following example, assume that you want to define a string length function (my_strlen) that handles long literals (CLOB) as well as short literals. On the SPARQL query side, this function can be referenced under the namespace of ouext, which is http://oracle.com/semtech/jena-adaptor/ext/user-def-function#.

PREFIX  ouext: <http://oracle.com/semtech/jena-adaptor/ext/user-def-function#>
SELECT ?subject ?object (ouext:my_strlen(?object) as ?obj1)
WHERE { ?subject dc:title ?object }

Inside the database, functions including my_strlen, my_strlen_cl, my_strlen_la, my_strlen_lt, and my_strlen_vt are defined to implement this capability. Conceptually, the return values of these functions are mapped as shown in Table 7-1.

A set of functions (five in all) is used to implement a user-defined function that can be referenced from SPARQL, because this aligns with the internal representation of an RDF resource (in MDSYS.RDF_VALUE$). There are five major columns describing an RDF resource in terms of its value, language, literal type, long value, and value type, and these five columns can be selected out using SEM_MATCH. In this context, a user-defined function simply converts one RDF resource that is represented by five columns to another RDF resource.

These functions are defined as follows:

create or replace function my_strlen(rdfvtyp in varchar2,
                              rdfltyp in varchar2,
                              rdflang in varchar2,
                              rdfclob in clob,
                              value   in varchar2
                              ) return varchar2
 as
   ret_val  varchar2(4000);
 begin
   -- value
   if (rdfvtyp = 'LIT') then
     if (rdfclob is null) then
       return length(value);
     else
       return dbms_lob.getlength(rdfclob);
     end if;
   else
     -- Assign -1 for non-literal values so that application can
     -- easily differentiate
     return '-1';
   end if;
 end;
 /
 
 create or replace function my_strlen_cl(rdfvtyp in varchar2,
                              rdfltyp in varchar2,
                              rdflang in varchar2,
                              rdfclob in clob,
                              value   in varchar2
                              ) return clob
 as
 begin
   return null;
 end;
 /
 
 create or replace function my_strlen_la(rdfvtyp in varchar2,
                              rdfltyp in varchar2,
                              rdflang in varchar2,
                              rdfclob in clob,
                              value   in varchar2
                              ) return varchar2
 as
 begin
   return null;
 end;
 /
 
 create or replace function my_strlen_lt(rdfvtyp in varchar2,
                              rdfltyp in varchar2,
                              rdflang in varchar2,
                              rdfclob in clob,
                              value   in varchar2
                              ) return varchar2
 as
   ret_val  varchar2(4000);
 begin
   -- literal type
   return 'http://www.w3.org/2001/XMLSchema#integer';
 end;
 /
 
 create or replace function my_strlen_vt(rdfvtyp in varchar2,
                              rdfltyp in varchar2,
                              rdflang in varchar2,
                              rdfclob in clob,
                              value   in varchar2
                              ) return varchar2
 as
   ret_val  varchar2(3);
 begin
   return 'LIT';
 end;
 /

User-defined functions can also accept a parameter of VARCHAR2 type. The following five functions together define a my_shorten_str function that accepts an integer (in VARCHAR2 form) for the substring length and returns the substring. (The substring in this example is 12 characters, and it must not be greater than 4000 bytes.)

-- SPARQL query that returns the first 12 characters of literal values.
-- 
PREFIX  ouext: <http://oracle.com/semtech/jena-adaptor/ext/user-def-function#>
SELECT (ouext:my_shorten_str(?object, "12") as ?obj1) ?subject
WHERE { ?subject dc:title ?object }
 
create or replace function my_shorten_str(rdfvtyp in varchar2,
                            rdfltyp in varchar2,
                            rdflang in varchar2,
                            rdfclob in clob,
                            value   in varchar2,
                            arg     in varchar2
                            ) return varchar2
as
 ret_val  varchar2(4000);
begin
 -- value
 if (rdfvtyp = 'LIT') then
   if (rdfclob is null) then
     return substr(value, 1, to_number(arg));
   else
     return dbms_lob.substr(rdfclob, to_number(arg), 1);
   end if;
 else
   return null;
 end if;
end;
/
 
create or replace function my_shorten_str_cl(rdfvtyp in varchar2,
                            rdfltyp in varchar2,
                            rdflang in varchar2,
                            rdfclob in clob,
                            value   in varchar2,
                            arg     in varchar2
                            ) return clob
as
 ret_val  clob;
begin
 -- lob
 return null;
end;
/
 
create or replace function my_shorten_str_la(rdfvtyp in varchar2,
                            rdfltyp in varchar2,
                            rdflang in varchar2,
                            rdfclob in clob,
                            value   in varchar2,
                            arg     in varchar2
                            ) return varchar2
as
 ret_val  varchar2(4000);
begin
 -- lang
 if (rdfvtyp = 'LIT') then
   return rdflang;
 else
   return null;
 end if;
end;
/
 
create or replace function my_shorten_str_lt(rdfvtyp in varchar2,
                            rdfltyp in varchar2,
                            rdflang in varchar2,
                            rdfclob in clob,
                            value   in varchar2,
                            arg     in varchar2
                            ) return varchar2
as
 ret_val  varchar2(4000);
begin
 -- literal type
 ret_val := rdfltyp;
 return ret_val;
end;
/
 
create or replace function my_shorten_str_vt(rdfvtyp in varchar2,
                            rdfltyp in varchar2,
                            rdflang in varchar2,
                            rdfclob in clob,
                            value   in varchar2,
                            arg     in varchar2
                            ) return varchar2
as
 ret_val  varchar2(3);
begin
 return 'LIT';
end;
/

7.10.1 Generating Contextual Information about a Path in a Graph

It is sometimes useful to see contextual information about a path in a graph, in addition to the path itself. The buildSurroundingSubGraph method in the SemNetworkAnalyst class can output a DOT file (graph description language file, extension .gv) into the specified Writer object. For each node in the path, up to ten direct neighbors are used to produce a surrounding subgraph for the path. Example 7-8 shows the usage, specifically the output from the analytical functions used in Example 7-6, "Performing Analytical functions on RDF Data".

nodeArray = sna.shortestPathDijkstra(nodeA, nodeD);
printNodeArray(nodeArray, psOut);
 
FileWriter dotWriter = new FileWriter("Shortest_Path_A_to_D.gv");
sna.buildSurroundingSubGraph(nodeArray, dotWriter);

The generated output DOT file from Example 7-8 is straightforward, as shown in the following example:

% cat Shortest_Path_A_to_D.gv
digraph { rankdir = LR; charset="utf-8"; 
 
"Rhttp://A" [ label="http://A" shape=rectangle,color=red,style = filled, ];
"Rhttp://B" [ label="http://B" shape=rectangle,color=red,style = filled, ];
"Rhttp://A" -> "Rhttp://B" [ label="http://likes"  color=red, style=bold, ];
"Rhttp://C" [ label="http://C" shape=rectangle,color=red,style = filled, ];
"Rhttp://A" -> "Rhttp://C" [ label="http://dislikes" ];
"Rhttp://D" [ label="http://D" shape=rectangle,color=red,style = filled, ];
"Rhttp://A" -> "Rhttp://D" [ label="http://differs" ];
"Rhttp://B" -> "Rhttp://C" [ label="http://likes"  color=red, style=bold, ];
"Rm1" [ label="m1" shape=ellipse,color=blue, ];
"Rhttp://B" -> "Rm1" [ label="http://dislikes" ];
"Rm1" -> "Rhttp://B" [ label="http://dislikes" ];
"Rhttp://C" -> "Rhttp://D" [ label="http://likes"  color=red, style=bold, ];
"Rhttp://E" [ label="http://E" shape=ellipse,color=blue, ];
"Rhttp://C" -> "Rhttp://E" [ label="http://knows" ];
"Rm1" -> "Rhttp://D" [ label="http://likes" ];
}

You can also use methods in the SemNetworkAnalyst and GraphOracleSem classes to produce more sophisticated visualization of the analytical function output.

You can convert the preceding DOT file into a variety of image formats. Figure 7-1 is an image representing the information in the preceding DOT file.

Figure 7-1 Visual Representation of Analytical Function Output

Description of "Figure 7-1 Visual Representation of Analytical Function Output"

7.11.1 Virtual Models Support

Virtual models (explained in Section 1.3.8) are specified in the GraphOracleSem constructor, and they are handled transparently. If a virtual model exists for the model-rulebase combination, it is used in query answering; if such a virtual model does not exist, it is created in the database.

The following example reuses an existing virtual model.

String modelName = "EX";
String m1 = "EX_1";
 
ModelOracleSem defaultModel = 
  ModelOracleSem.createOracleSemModel(oracle, modelName);
 
// create these models in case they don't exist
ModelOracleSem model1 = ModelOracleSem.createOracleSemModel(oracle, m1);
 
String vmName = "VM_" + modelName;
 
 
//create a virtual model containing EX and EX_1
oracle.executeCall(
"begin sem_apis.create_virtual_model(?,sem_models('"+ m1 + "','"+ modelName+"'),null); end;",vmName);
 
String[] modelNames = {m1};
String[] rulebaseNames = {};
 
Attachment attachment = Attachment.createInstance(modelNames, rulebaseNames, 
InferenceMaintenanceMode.NO_UPDATE, QueryOptions.ALLOW_QUERY_VALID_AND_DUP);
 
// vmName is passed to the constructor, so GraphOracleSem will use the virtual 
// model named vmname (if the current user has read privileges on it)
GraphOracleSem graph = new GraphOracleSem(oracle, modelName, attachment, vmName);
graph.add(Triple.create(Node.createURI("urn:alice"),
                        Node.createURI("http://xmlns.com/foaf/0.1/mbox"),
                        Node.createURI("mailto:alice@example")));
ModelOracleSem model = new ModelOracleSem(graph);          
 
String queryString =
 
   " SELECT ?subject ?object WHERE { ?subject ?p ?object } ";
 
Query query = QueryFactory.create(queryString) ;
QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
 
try {
   ResultSet results = qexec.execSelect() ;
   for ( ; results.hasNext() ; ) {
      QuerySolution soln = results.nextSolution() ;
      psOut.println("soln " + soln);
   }
} 
finally { 
   qexec.close() ; 
}
 
OracleUtils.dropSemanticModel(oracle, modelName);
OracleUtils.dropSemanticModel(oracle, m1);
 
oracle.dispose();

You can also use the GraphOracleSem constructor to create a virtual model, as in the following example:

GraphOracleSem graph = new GraphOracleSem(oracle, modelName, attachment, true);

In this example, the fourth parameter (true) specifies that a virtual model needs to be created for the specified modelName and attachment.

7.11.2 Connection Pooling Support

Oracle Database Connection Pooling is provided through the support for Apache Jena OraclePool class. Once this class is initialized, it can return Oracle objects out of its pool of available connections. Oracle objects are essentially database connection wrappers. After dispose is called on the Oracle object, the connection is returned to the pool. More information about using OraclePool can be found in the API reference information (Javadoc).

The following example sets up an OraclePool object with five (5) initial connections.

public static void main(String[] args) throws Exception
  {      
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
 
    // test with connection properties 
    java.util.Properties prop = new java.util.Properties();
    prop.setProperty("MinLimit", "2");     // the cache size is 2 at least 
    prop.setProperty("MaxLimit", "10");
    prop.setProperty("InitialLimit", "2"); // create 2 connections at startup
    prop.setProperty("InactivityTimeout", "1800");    //  seconds
    prop.setProperty("AbandonedConnectionTimeout", "900");  //  seconds
    prop.setProperty("MaxStatementsLimit", "10");
    prop.setProperty("PropertyCheckInterval", "60"); // seconds
 
    System.out.println("Creating OraclePool");
    OraclePool op = new OraclePool(szJdbcURL, szUser, szPasswd, prop, 
               "OracleSemConnPool");
    System.out.println("Done creating OraclePool");
 
    // grab an Oracle and do something with it
    System.out.println("Getting an Oracle from OraclePool");
    Oracle oracle = op.getOracle();
    System.out.println("Done");
    System.out.println("Is logical connection:" +
        oracle.getConnection().isLogicalConnection());
    GraphOracleSem g = new GraphOracleSem(oracle, szModelName);
    g.add(Triple.create(Node.createURI("u:John"), 
                        Node.createURI("u:parentOf"), 
                        Node.createURI("u:Mary")));
    g.close();
    // return the Oracle back to the pool
    oracle.dispose();
    
    // grab another Oracle and do something else 
    System.out.println("Getting an Oracle from OraclePool");
    oracle = op.getOracle();
    System.out.println("Done");
    System.out.println("Is logical connection:" +
        oracle.getConnection().isLogicalConnection());
    g = new GraphOracleSem(oracle, szModelName);
    g.add(Triple.create(Node.createURI("u:John"), 
                        Node.createURI("u:parentOf"), 
                        Node.createURI("u:Jack")));
    g.close();
    
    OracleUtils.dropSemanticModel(oracle, szModelName); 
    
    // return the Oracle object back to the pool
    oracle.dispose();
}

7.11.3 Semantic Model PL/SQL Interfaces

Several semantic PL/SQL subprograms are available through the support for Apache Jena. Table 7-2 lists the subprograms and their corresponding Java class and methods.

For information about these PL/SQL utility subprograms, see the reference information in Chapter 11. For information about the corresponding Java class and methods, see the RDF Semantic Graph support for Apache Jena API Reference documentation (Javadoc).

7.11.4 Inference Options

You can add options to entailment calls by using the following methods in the Attachment class (in package oracle.spatial.rdf.client.jena):

public void setUseLocalInference(boolean useLocalInference)
public boolean getUseLocalInference()
 
public void setDefGraphForLocalInference(String defaultGraphName)
public String getDefGraphForLocalInference()
 
public String getInferenceOption()
public void setInferenceOption(String inferenceOption)

For more information about these methods, see the Javadoc.

Example 7-9 enables parallel inference (with a degree of 4) and RAW format when creating an entailment. The example also uses the performInference method to create the entailment (comparable to using the SEM_APIS.CREATE_ENTAILMENT PL/SQL procedure).

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import com.hp.hpl.jena.util.iterator.*;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.update.*;
import com.hp.hpl.jena.sparql.core.DatasetImpl;
 
public class TestNewInference
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
 
    PrintStream psOut = System.out;
 
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    
    String szTBoxName = "test_new_tbox";
    {
      // First construct a TBox and load a few axioms
      ModelOracleSem modelTBox = ModelOracleSem.createOracleSemModel(oracle, szTBoxName);
      String insertString =  
        " PREFIX my:  <http://my.com/> " +
        " PREFIX rdfs:  <http://www.w3.org/2000/01/rdf-schema#> " +
        " INSERT DATA "                                     +
        " { my:C1  rdfs:subClassOf my:C2 .                " +
        "   my:C2  rdfs:subClassOf my:C3 .                " +
        "   my:C3  rdfs:subClassOf my:C4 .                " +
        " }   ";
      UpdateAction.parseExecute(insertString,  modelTBox);
      modelTBox.close();
    }
 
    String szABoxName = "test_new_abox";
    {
      // Construct an ABox and load a few quads
      ModelOracleSem modelABox = ModelOracleSem.createOracleSemModel(oracle, szABoxName);
      DatasetGraphOracleSem dataset = DatasetGraphOracleSem.createFrom(modelABox.getGraph());
      modelABox.close();
 
      String insertString =  
        " PREFIX my:    <http://my.com/> " +
        " PREFIX rdf:   <http://www.w3.org/1999/02/22-rdf-syntax-ns#> " +
        " INSERT DATA                                                 " +
        " { GRAPH my:G1 { my:I1  rdf:type my:C1 .                     " +
        "                 my:I2  rdf:type my:C2 .                     " +
        "               }                                             " +
        " };                                                          " +
        " INSERT DATA                                                 " +
        " { GRAPH my:G2 { my:J1  rdf:type my:C3 .                     " +
        "               }                                             " +
        " }    ";
      UpdateAction.parseExecute(insertString,  dataset);
      dataset.close();
    }
 
 
    String[] attachedModels = new String[1];
    attachedModels[0] = szTBoxName;
 
    String[] attachedRBs = {"OWL2RL"};
 
    Attachment attachment = Attachment.createInstance(
        attachedModels, attachedRBs,
        InferenceMaintenanceMode.NO_UPDATE,
        QueryOptions.ALLOW_QUERY_INVALID);
 
    // We are going to run named graph based local inference
    attachment.setUseLocalInference(true);
 
    // Set the default graph (TBox)
    attachment.setDefGraphForLocalInference(szTBoxName);
 
    // Set the inference option to use parallel inference 
    // with a degree of 4, and RAW format.
    attachment.setInferenceOption("DOP=4,RAW8=T");
 
    GraphOracleSem graph = new GraphOracleSem(
        oracle, 
        szABoxName, 
        attachment
        );
    DatasetGraphOracleSem dsgos = DatasetGraphOracleSem.createFrom(graph);
    graph.close();
 
    // Invoke create_entailment PL/SQL API
    dsgos.performInference();
 
    psOut.println("TestNewInference: # of inferred graph " + 
        Long.toString(dsgos.getInferredGraphSize()));
 
    String queryString = 
      " SELECT ?g ?s ?p ?o WHERE {  GRAPH ?g {?s ?p ?o } } " ;
 
    Query query = QueryFactory.create(queryString, Syntax.syntaxARQ);
    QueryExecution qexec = QueryExecutionFactory.create(
        query, DatasetImpl.wrap(dsgos));
    ResultSet results = qexec.execSelect();
 
    ResultSetFormatter.out(psOut, results);
 
    dsgos.close();
    oracle.dispose();
  }
}

The output of Example 7-9 is as follows.

TestNewInference: # of inferred graph 9
 
--------------------------------------------------------------------------------------------------------------------
| g                  | s                  | p                                                 | o                  |
====================================================================================================================
| <http://my.com/G1> | <http://my.com/I2> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C3> |
| <http://my.com/G1> | <http://my.com/I2> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C2> |
| <http://my.com/G1> | <http://my.com/I2> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C4> |
| <http://my.com/G1> | <http://my.com/I1> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C3> |
| <http://my.com/G1> | <http://my.com/I1> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C1> |
| <http://my.com/G1> | <http://my.com/I1> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C2> |
| <http://my.com/G1> | <http://my.com/I1> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C4> |
| <http://my.com/G2> | <http://my.com/J1> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C3> |
| <http://my.com/G2> | <http://my.com/J1> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://my.com/C4> |
--------------------------------------------------------------------------------------------------------------------

For information about using OWL inferencing, see Section 2.2.

7.11.5 PelletInfGraph Class Support Deprecated

The support for the PelletInfGraph class within the support for Apache Jena is deprecated. You should instead use the more optimized Oracle/Pellet integration through the PelletDb OWL 2 reasoner for Oracle Database. (For information about PelletDb, see http://clarkparsia.com/pelletdb/.)

7.12.1 Using prepareBulk in Parallel (Multithreaded) Mode

Example 7-10, "Loading Data into the Staging Table (prepareBulk)" provided a way to load, sequentially, a set of files under a file system directory to an Oracle Database table (staging table). Example 7-14 loads, concurrently, a set of files to an Oracle table (staging table). The degree of parallelism is controlled by the input parameter iMaxThreads.

On a balanced hardware setup with 4 or more CPU cores, setting iMaxThreads to 8 (or 16) can improve significantly the speed of prepareBulk operation when there are many data files to be processed.

public void testPrepareInParallel(String jdbcUrl, String user,
                       String password, String modelName,
                       String lang,
                       String tbs,
                       String dirname,
                       int iMaxThreads,
                       PrintStream psOut)
   throws SQLException, IOException,  InterruptedException
 {
   File dir = new File(dirname);
   File[] files = dir.listFiles();

   // create a set of physical Oracle connections and graph objects
   Oracle[] oracles = new Oracle[iMaxThreads];
   GraphOracleSem[] graphs = new GraphOracleSem[iMaxThreads];
   for (int idx = 0; idx < iMaxThreads; idx++) {
     oracles[idx] = new Oracle(jdbcUrl, user, password);
     graphs[idx] = new GraphOracleSem(oracles[idx], modelName);
   }

   PrepareWorker[] workers = new PrepareWorker[iMaxThreads];
   Thread[] threads = new Thread[iMaxThreads];
   for (int idx = 0; idx < iMaxThreads; idx++) {
     workers[idx] = new PrepareWorker(
         graphs[idx],
         files,
         idx,
         iMaxThreads,
         lang,
         tbs,
         psOut
         );
     threads[idx] = new Thread(workers[idx], workers[idx].getName());
     psOut.println("testPrepareInParallel: PrepareWorker " + idx + " running");
     threads[idx].start();
   }

   psOut.println("testPrepareInParallel: all threads started");

   for (int idx = 0; idx < iMaxThreads; idx++) {
     threads[idx].join();
   }
   for (int idx = 0; idx < iMaxThreads; idx++) {
     graphs[idx].close();
     oracles[idx].dispose();
   }
 }

 static class PrepareWorker implements Runnable
 {
   GraphOracleSem graph = null;
   int idx;
   int threads;
   File[] files = null;
   String lang = null;
   String tbs  = null;
   PrintStream psOut;

   public void run()
   {
     long lStartTime = System.currentTimeMillis();
     for (int idxFile = idx; idxFile < files.length; idxFile += threads) {
       File file = files[idxFile];
       try {
         FileInputStream fis = new FileInputStream(file);
         graph.getBulkUpdateHandler().prepareBulk(
             fis,
             "http://base.com/",
             lang,
             tbs,
             null,                   // flags
             new MyListener(psOut),  // listener
             null                    // table name
             );
         fis.close();
       }
       catch (Exception e) {
         psOut.println("PrepareWorker: thread ["+getName()+"] error "+ e.getMessage());
       }
       psOut.println("PrepareWorker: thread ["+getName()+"] done to "
           + idxFile + ", file = " + file.toString()
           + " in (ms) " + (System.currentTimeMillis() - lStartTime));
     }
   }

   public PrepareWorker(GraphOracleSem graph,
                        File[] files,
                        int idx,
                        int threads,
                        String lang,
                        String tbs,
                        PrintStream psOut)
   {
     this.graph   = graph;
     this.files   = files;
     this.psOut   = psOut;
     this.idx     = idx;
     this.threads = threads;
     this.files   = files;
     this.lang    = lang;
     this.tbs     = tbs ;
   }

   public String getName()
   {
     return "PrepareWorker" + idx;
   }
 } 
 
 static class MyListener implements StatusListener 
 {
   PrintStream m_ps = null;
   public MyListener(PrintStream ps) { m_ps = ps; }
   long lLastBatch = 0;

   public void statusChanged(long count)
   {
     if (count - lLastBatch >= 10000) {
       m_ps.println("process to " + Long.toString(count));
       lLastBatch = count;
     }
   }

   public int illegalStmtEncountered(Node graphNode, Triple triple, long count)
   {
     m_ps.println("hit illegal statement with object " + triple.getObject().toString());
     return 0; // skip it
   }
 }

7.12.2 Handling Illegal Syntax During Data Loading

You can skip illegal triples and quads when using prepareBulk. This feature is useful if the source RDF data may contain syntax errors. In Example 7-15, a customized implementation of the StatusListener interface (defined in package oracle.spatial.rdf.client.jena) is passed as a parameter to prepareBulk. In this example, the illegalStmtEncountered method prints the object field of the illegal triple, and returns 0 so that prepareBulk can skip that illegal triple and move on.

....
 
Oracle oracle = new Oracle(jdbcUrl, user, password);
GraphOracleSem graph = new GraphOracleSem(oracle, modelName);
PrintStream psOut = System.err;
 
graph.getBulkUpdateHandler().prepareBulk(
  new FileInputStream(rdfDataFilename),
  "http://base.com/",    // base 
  lang,                  // data format, can be "N-TRIPLES" "RDF/XML" ...
  tbs,                   // tablespace name
  null,                  // flags
  new MyListener(psOut), // call back to show progress and also process illegal triples/quads
  null,                  // tableName, if null use default names
  false                  // truncate existing staging tables
  );
 
 graph.close();
 oracle.dispose();
 .... 
 
 // A customized StatusListener interface implementation
  public class MyListener implements StatusListener
 {
   PrintStream m_ps = null;
   public MyListener(PrintStream ps) { m_ps = ps; }
 
   public void statusChanged(long count)
   {
     // m_ps.println("process to " + Long.toString(count));
   }
 
  public int illegalStmtEncountered(Node graphNode, Triple triple, long count)
  {
    m_ps.println("hit illegal statement with object " + triple.getObject().toString());
    return 0; // skip it
  }
 }

7.15.1 BOUND or !BOUND Instead of EXISTS or NOT EXISTS

For better performance, use BOUND or !BOUND instead of EXISTS or NOT EXISTS.

7.15.2 SPARQL 1.1 SELECT Expressions

You can use SPARQL 1.1 SELECT expressions without any significant performance overhead, even if the function is not currently supported within Oracle Database. Examples include the following:

-- Quyery using MD5 and SHA1 functions
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX xsd:  <http://www.w3.org/2001/XMLSchema#>
PREFIX eg:   <http://biometrics.example/ns#>
SELECT ?name (md5(?name) as ?name_in_md5) (sha1(?email) as ?sha1) 
WHERE 
{ 
  ?x foaf:name  ?name ; eg:email ?email .
}

-- Quyery using CONCAT function
PREFIX foaf:   <http://xmlns.com/foaf/0.1/>
SELECT ( CONCAT(?G, " ", ?S) AS ?name )
WHERE  
{ 
  ?P foaf:givenName ?G ; foaf:surname ?S 
}

7.15.3 Syntax Involving Bnodes (Blank Nodes)

Syntax involving bnodes can be used freely in query patterns. For example, the following bnode-related syntax is supported at the parser level, so each is equivalent to its full triple-query-pattern-based version.

:x :q [ :p "v" ] .
 
(1 ?x 3 4) :p "w" .
 
(1 [:p :q] ( 2 ) ) .

7.15.4 Limit in the SERVICE Clause

When writing a SPARQL 1.1 federated query, you can set a limit on returned rows in the subquery inside the SERVICE clause. This can effectively constrain the amount of data to be transported between the local repository and the remote SPARQL endpoint.

For example, the following query specifies limit 100 in the subquery in the SERVICE clause:

PREFIX : <http://example.com/>
SELECT ?s ?o 
 WHERE 
     { 
       ?s :name "CA"  
       SERVICE <http://REMOTE_SPARQL_ENDPOINT_HERE>
          {
             select ?s  ?o 
                 {?s :info ?o} 
              limit 100 
           } 
     }

7.15.5 OracleGraphWrapperForOntModel Class for Better Performance

The Jena OntModel class lets you create, modify, and analyze an ontology stored in a Jena model. However, the OntModel implementation is not optimized for semantic data stored in a database. This results in suboptimal performance when using OntModel with an Oracle model. Therefore, the class OracleGraphWrapperForOntModel has been created to alleviate this performance issue.

The OracleGraphWrapperForOntModel class implements the Jena Graph interface and represents a graph backed by an Oracle RDF/OWL model that is meant for use with the Jena OntModel API. The OracleGraphWrapperForOntModel class uses two semantic stores in a hybrid approach for persisting changes and responding to queries. Both semantic stores contain the same data, but one resides in memory while the other resides in the Oracle database.

When queried through OntModel, the OracleGraphWrapperForOntModel graph runs the queries against the in-memory store to improve performance. However, the OracleGraphWrapperForOntModel class persists changes made through OntModel, such as adding or removing classes, by applying changes to both stores.

Due to its hybrid approach, an OracleGraphWrapperForOntModel graph requires that sufficient memory be allocated to the JVM to store a copy of the ontology in memory. In internal experiments, it was found that an ontology with approximately 3 million triples requires 6 or more GB of physical memory.

Example 7-16 shows how to use the OntModel APIs with an existing ontology stored in an Oracle model.

// Set up connection to Oracle semantic store and the Oracle model
// containing the ontology
Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
GraphOracleSem oracleGraph = new GraphOracleSem(oracle, szModelName);
 
// Create a new hybrid graph using the oracle graph to persist
// changes.  This method will copy all the data from the oracle graph
// into an in-memory graph, which may significantly increase JVM memory
// usage.
Graph hybridGraph = OracleGraphWrapperForOntModel.getInstance(oracleGraph);
 
// Build a model around the hybrid graph and wrap the model with Jena's
// OntModel
Model model = ModelFactory.createModelForGraph(hybridGraph);
OntModel ontModel = ModelFactory.createOntologyModel(ontModelSpec, model);
 
// Perform operations on the ontology
OntClass personClass = ontModel.createClass("<http://someuri/person>");
ontModel.createIndividual(personClass);
 
// Close resources (will also close oracleGraph)!
hybridGraph.close();
ontModel.close();

Note that any OntModel object created using OracleGraphWrapperForOntModel will not reflect changes made to the underlying Oracle model by another process, through a separate OntModel, or through a separate Oracle graph referencing the same underlying model. All changes to an ontology should go through a single OntModel object and its underlying OracleGraphWrapperForOntModel graph until the model or graph have been closed.

If the default in-memory semantic store used by OracleGraphWrapperForOntModel is not sufficient for an ontology and system, the class provides an interface for specifying a custom graph to use as the in-memory store. Example 7-17 shows how to create an OracleGraphWrapperForOntModel that uses a custom in-memory graph to answer queries from OntModel.

// Set up connection to Oracle semantic store and the Oracle model
// containing the ontology
Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
GraphOracleSem oracleGraph = new GraphOracleSem(oracle, szModelName);
 
// Create a custom in-memory graph to use instead of the default
// Jena in-memory graph for quickly answering OntModel queries.
// Note that this graph does not *need* to be in-memory, but in-memory
// is preferred.
GraphBase queryGraph = new CustomInMemoryGraphImpl();
 
// Create a new hybrid graph using the oracle graph to persist
// changes and the custom in-memory graph to answer queries. 
// Also set the degree of parallelism to use when copying data from
// the oracle graph to the querying graph.
int degreeOfParallelism = 4;
Graph hybridGraph = OracleGraphWrapperForOntModel.getInstance(oracleGraph, queryGraph, degreeOfParallelism);
 
// Build a model and wrap the model with Jena's OntModel
Model model = ModelFactory.createModelForGraph(hybridGraph);
OntModel ontModel = ModelFactory.createOntologyModel(ontModelSpec, model);
 
// Perform operations on the ontology
// ...
 
// Close resources (will close oracleGraph and queryGraph)!
hybridGraph.close();
ontModel.close();

7.16.1 Test.java: Query Family Relationships

Example 7-18 specifies that John is the father of Mary, and it selects and displays the subject and object in each fatherOf relationship

import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.query.*;
public class Test {
 
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
          
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    Model model = ModelOracleSem.createOracleSemModel(
      oracle, szModelName);
 
    model.getGraph().add(Triple.create(
          Node.createURI("http://example.com/John"),
          Node.createURI("http://example.com/fatherOf"),
          Node.createURI("http://example.com/Mary")));
    Query query = QueryFactory.create(
        "select ?f ?k WHERE {?f <http://example.com/fatherOf> ?k .}");
    QueryExecution qexec = QueryExecutionFactory.create(query, model);
    ResultSet results = qexec.execSelect();
    ResultSetFormatter.out(System.out, results, query);
    model.close();
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-18, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
 
---------------------------------------------------------
| f                         | k                         |
=========================================================
| <http://example.com/John> | <http://example.com/Mary> |
---------------------------------------------------------

7.16.2 Test6.java: Load OWL Ontology and Perform OWLPrime inference

Example 7-19 loads an OWL ontology and performs OWLPrime inference. Note that the OWL ontology is in RDF/XML format, and after it is loaded into Oracle it will be serialized out in N-TRIPLE form. The example also queries for the number of asserted and inferred triples.

The ontology in this example can be retrieved from http://swat.cse.lehigh.edu/onto/univ-bench.owl, and it describes roles, resources, and relationships in a university environment.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import oracle.spatial.rdf.client.jena.*;
public class Test6 {
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    Model model = ModelOracleSem.createOracleSemModel(oracle, szModelName);
        
    // load UNIV ontology
    InputStream in = FileManager.get().open("./univ-bench.owl" );
    model.read(in, null);
    OutputStream os = new FileOutputStream("./univ-bench.nt");
    model.write(os, "N-TRIPLE");
    os.close();
 
    String queryString =
      " SELECT ?subject ?prop ?object WHERE { ?subject ?prop ?object } ";
 
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
 
    try {
      int iTriplesCount = 0;
      ResultSet results = qexec.execSelect() ;
      for ( ; results.hasNext() ; ) {
        QuerySolution soln = results.nextSolution() ;
        iTriplesCount++;
      }
      System.out.println("Asserted  triples count: " + iTriplesCount);
    } 
    finally { 
      qexec.close() ; 
    }
    
    Attachment attachment = Attachment.createInstance(
        new String[] {}, "OWLPRIME",
        InferenceMaintenanceMode.NO_UPDATE, QueryOptions.DEFAULT);
 
    GraphOracleSem graph = new GraphOracleSem(oracle, szModelName, attachment);
    graph.analyze();
    graph.performInference();
 
    query = QueryFactory.create(queryString) ;
    qexec = QueryExecutionFactory.create(query,new ModelOracleSem(graph)) ;
 
    try {
      int iTriplesCount = 0;
      ResultSet results = qexec.execSelect() ;
      for ( ; results.hasNext() ; ) {
        QuerySolution soln = results.nextSolution() ;
        iTriplesCount++;
      }
      System.out.println("Asserted + Infered triples count: " + iTriplesCount);
    } 
    finally { 
      qexec.close() ; 
    }
    model.close();    
 
    OracleUtils.dropSemanticModel(oracle, szModelName);    
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-19, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test6.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test6 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
Asserted  triples count: 294
Asserted + Infered triples count: 341

Note that this output reflects an older version of the LUBM ontology. The latest version of the ontology has more triples.

7.16.3 Test7.java: Bulk Load OWL Ontology and Perform OWLPrime inference

Example 7-20 loads the same OWL ontology as in Section 7.16.2, but stored in a local file using Bulk Loader. Ontologies can also be loaded using an incremental and batch loader; these two methods are also listed in the example for completeness.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.rdf.model.*;
import com.hp.hpl.jena.util.*;
import oracle.spatial.rdf.client.jena.*;
 
public class Test7 
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    // in memory Jena Model
    Model model = ModelFactory.createDefaultModel();
    InputStream is = FileManager.get().open("./univ-bench.owl");
    model.read(is, "", "RDF/XML");
    is.close();
 
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem modelDest = ModelOracleSem.createOracleSemModel(oracle, 
szModelName);
 
    GraphOracleSem g = modelDest.getGraph();
    g.dropApplicationTableIndex();
 
    int method = 2; // try bulk loader
    String tbs = "SYSAUX"; // can be customized
    if (method == 0) {
      System.out.println("start incremental");
      modelDest.add(model);
      System.out.println("end size " + modelDest.size());
    }
    else if (method == 1) {
      System.out.println("start batch load");
      g.getBulkUpdateHandler().addInBatch(
          GraphUtil.findAll(model.getGraph()), tbs);
      System.out.println("end size " + modelDest.size());
    }
    else {
      System.out.println("start bulk load");
      g.getBulkUpdateHandler().addInBulk(
          GraphUtil.findAll(model.getGraph()), tbs);
      System.out.println("end size " + modelDest.size());
    }
    g.rebuildApplicationTableIndex();
 
    long lCount = g.getCount(Triple.ANY);
    System.out.println("Asserted  triples count: " + lCount);
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-20, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test7.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test7 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
start bulk load
end size 293
Asserted  triples count: 293

Note that this output reflects an older version of the LUBM ontology. The latest version of the ontology has more triples.

7.16.4 Test8.java: SPARQL OPTIONAL Query

Example 7-21 shows a SPARQL OPTIONAL query. It inserts triples that postulate the following:

• John is a parent of Mary.

• John is a parent of Jack.

• Mary is a parent of Jill.

It then finds parent-child relationships, optionally including any grandchild (gkid) relationships.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
 
public class Test8 
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, 
szModelName);
    GraphOracleSem g = model.getGraph();
 
    g.add(Triple.create(
          Node.createURI("u:John"), Node.createURI("u:parentOf"), 
Node.createURI("u:Mary")));
    g.add(Triple.create(
          Node.createURI("u:John"), Node.createURI("u:parentOf"), 
Node.createURI("u:Jack")));
    g.add(Triple.create(
          Node.createURI("u:Mary"), Node.createURI("u:parentOf"), 
Node.createURI("u:Jill")));
        
    String queryString =
  " SELECT ?s ?o ?gkid " +
  " WHERE { ?s <u:parentOf> ?o . OPTIONAL {?o <u:parentOf> ?gkid }} ";
 
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
 
    try {
      int iMatchCount = 0;
      ResultSet results = qexec.execSelect() ;
      ResultSetFormatter.out(System.out, results, query);
    } 
    finally { 
      qexec.close() ; 
    }
    model.close();    
 
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-21, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test8.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test8 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
----------------------------------
| s        | o        | gkid     |
==================================
| <u:John> | <u:Mary> | <u:Jill> |
| <u:Mary> | <u:Jill> |          |
| <u:John> | <u:Jack> |          |
---------------------------------- 

7.16.5 Test9.java: SPARQL Query with LIMIT and OFFSET

Example 7-22 shows a SPARQL query with LIMIT and OFFSET. It inserts triples that postulate the following:

• John is a parent of Mary.

• John is a parent of Jack.

• Mary is a parent of Jill.

It then finds one parent-child relationship (LIMIT 1), skipping the first two parent-child relationships encountered (OFFSET 2), and optionally includes any grandchild (gkid) relationships for the one found.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
public class Test9 
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, 
szModelName);
    GraphOracleSem g = model.getGraph();
 
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"),
                    Node.createURI("u:Mary")));
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"),
                    Node.createURI("u:Jack")));
    g.add(Triple.create(Node.createURI("u:Mary"), Node.createURI("u:parentOf"),              
                    Node.createURI("u:Jill")));
        
    String queryString =
      " SELECT ?s ?o ?gkid " +
      " WHERE { ?s <u:parentOf> ?o . OPTIONAL {?o <u:parentOf> ?gkid }} " +
      " LIMIT 1 OFFSET 2";
 
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
 
    int iMatchCount = 0;
    ResultSet results = qexec.execSelect() ;
    ResultSetFormatter.out(System.out, results, query);
    qexec.close() ; 
    model.close();    
 
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-22, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test9.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test9 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
------------------------------
| s        | o        | gkid |
==============================
| <u:John> | <u:Jack> |      |
------------------------------ 

7.16.6 Test10.java: SPARQL Query with TIMEOUT and DOP

Example 7-23 shows the SPARQL query from Section 7.16.5 with additional features, including a timeout setting (TIMEOUT=1, in seconds) and parallel execution setting (DOP=4).

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
 
public class Test10 {
  public static void main(String[] args) throws Exception  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, szModelName);
    GraphOracleSem g = model.getGraph();
 
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
                            Node.createURI("u:Mary")));
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
                        Node.createURI("u:Jack")));
    g.add(Triple.create(Node.createURI("u:Mary"), Node.createURI("u:parentOf"), 
                        Node.createURI("u:Jill")));
    String queryString =
        " PREFIX ORACLE_SEM_FS_NS: <http://oracle.com/semtech#dop=4,timeout=1> " 
      + " SELECT ?s ?o ?gkid WHERE { ?s <u:parentOf> ?o . " 
      + " OPTIONAL {?o <u:parentOf> ?gkid }} "
      + " LIMIT 1 OFFSET 2";
 
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
 
    int iMatchCount = 0;
    ResultSet results = qexec.execSelect() ;
    ResultSetFormatter.out(System.out, results, query);
    qexec.close() ; 
    model.close();    
 
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-23, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test10.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test10 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
------------------------------
| s        | o        | gkid |
==============================
| <u:John> | <u:Jack> |      |
------------------------------

7.16.7 Test11.java: Query Involving Named Graphs

Example 7-24 shows a query involving named graphs. It involves a default graph that has information about named graph URIs and their publishers. The query finds graph names, their publishers, and within each named graph finds the mailbox value using the foaf:mbox predicate.

import java.io.*;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.sparql.core.*;
import com.hp.hpl.jena.query.*;
import oracle.spatial.rdf.client.jena.*;
 
public class Test11
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    GraphOracleSem graph = new GraphOracleSem(oracle, szModelName);
    DatasetGraphOracleSem dataset = DatasetGraphOracleSem.createFrom(graph);
    
    // don't need the GraphOracleSem anymore, release resources
    graph.close();
    
    // add data to the default graph
    dataset.add(new Quad(
          Quad.defaultGraphIRI, // specifies default graph
          Node.createURI("http://example.org/bob"),
          Node.createURI("http://purl.org/dc/elements/1.1/publisher"),
          Node.createLiteral("Bob Hacker")));
    dataset.add(new Quad(
          Quad.defaultGraphIRI, // specifies default graph
          Node.createURI("http://example.org/alice"),
          Node.createURI("http://purl.org/dc/elements/1.1/publisher"),
          Node.createLiteral("alice Hacker")));
    
    // add data to the bob named graph
    dataset.add(new Quad(
          Node.createURI("http://example.org/bob"), // graph name
          Node.createURI("urn:bob"),
          Node.createURI("http://xmlns.com/foaf/0.1/name"),
          Node.createLiteral("Bob")));
    dataset.add(new Quad(
          Node.createURI("http://example.org/bob"), // graph name
          Node.createURI("urn:bob"),
          Node.createURI("http://xmlns.com/foaf/0.1/mbox"),
          Node.createURI("mailto:bob@example")));
    
    // add data to the alice named graph
    dataset.add(new Quad(
          Node.createURI("http://example.org/alice"), // graph name
          Node.createURI("urn:alice"),
          Node.createURI("http://xmlns.com/foaf/0.1/name"),
          Node.createLiteral("Alice")));
    dataset.add(new Quad(
          Node.createURI("http://example.org/alice"), // graph name
          Node.createURI("urn:alice"),
          Node.createURI("http://xmlns.com/foaf/0.1/mbox"),
          Node.createURI("mailto:alice@example")));
    
    DataSource ds = DatasetFactory.create(dataset);
    
    String queryString =  
          " PREFIX foaf: <http://xmlns.com/foaf/0.1/> "
        + " PREFIX dc: <http://purl.org/dc/elements/1.1/> "
        + " SELECT ?who ?graph ?mbox "
        + " FROM NAMED <http://example.org/alice> "
        + " FROM NAMED <http://example.org/bob> "
        + " WHERE "
        + " { " 
        + "    ?graph dc:publisher ?who . "
        + "    GRAPH ?graph { ?x foaf:mbox ?mbox } "
        + " } ";
    
    Query query = QueryFactory.create(queryString);
    QueryExecution qexec = QueryExecutionFactory.create(query, ds);
    
    ResultSet results = qexec.execSelect();
    ResultSetFormatter.out(System.out, results, query);
    
    qexec.close();
    dataset.close();
    
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-24, as well as the expected output of the java command.

javac -classpath ./:./jena-2.6.4.jar:./sdordfclient.jar:./ojdbc6.jar:./slf4j-api-1.5.8.jar:./slf4j-log4j12-1.5.8.jar:./arq-2.8.8.jar:./xercesImpl-2.7.1.jar Test11.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test11 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
------------------------------------------------------------------------
| who            | graph                      | mbox                   |
========================================================================
| "alice Hacker" | <http://example.org/alice> | <mailto:alice@example> |
| "Bob Hacker"   | <http://example.org/bob>   | <mailto:bob@example>   |
------------------------------------------------------------------------ 

7.16.8 Test12.java: SPARQL ASK Query

Example 7-25 shows a SPARQL ASK query. It inserts a triple that postulates that John is a parent of Mary. It then finds whether John is a parent of Mary.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
public class Test12
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, 
          szModelName);
    GraphOracleSem g = model.getGraph();
 
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
                        Node.createURI("u:Mary")));
    String queryString = " ASK { <u:John> <u:parentOf> <u:Mary> } ";
 
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
    boolean b = qexec.execAsk();
    System.out.println("ask result = " + ((b)?"TRUE":"FALSE"));
    qexec.close() ; 
    
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-25, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test12.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test12 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
ask result = TRUE

7.16.9 Test13.java: SPARQL DESCRIBE Query

Example 7-26 shows a SPARQL DESCRIBE query. It inserts triples that postulate the following:

• John is a parent of Mary.

• John is a parent of Jack.

• Amy is a parent of Jack.

It then finds all relationships that involve any parents of Jack.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
 
public class Test13
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, szModelName);
    GraphOracleSem g = model.getGraph();
 
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
                    Node.createURI("u:Mary")));
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
 Node.createURI("u:Jack")));
    g.add(Triple.create(Node.createURI("u:Amy"), Node.createURI("u:parentOf"), 
 Node.createURI("u:Jack")));
    String queryString = " DESCRIBE ?x WHERE {?x <u:parentOf> <u:Jack>}";
 
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
    Model m = qexec.execDescribe();
    System.out.println("describe result = " + m.toString());
 
    qexec.close() ; 
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-26, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test13.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test13 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
describe result = <ModelCom   {u:Amy @u:parentOf u:Jack; u:John @u:parentOf u:Jack; u:John @u:parentOf u:Mary} | >

7.16.10 Test14.java: SPARQL CONSTRUCT Query

Example 7-27 shows a SPARQL CONSTRUCT query. It inserts triples that postulate the following:

• John is a parent of Mary.

• John is a parent of Jack.

• Amy is a parent of Jack.

• Each parent loves all of his or her children.

It then constructs an RDF graph with information about who loves whom.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
 
public class Test14
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, szModelName);
    GraphOracleSem g = model.getGraph();
 
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
 Node.createURI("u:Mary")));
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
 Node.createURI("u:Jack")));
    g.add(Triple.create(Node.createURI("u:Amy"), Node.createURI("u:parentOf"), 
 Node.createURI("u:Jack")));
    String queryString = " CONSTRUCT { ?s <u:loves> ?o } WHERE {?s <u:parentOf> ?o}";
 
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
    Model m = qexec.execConstruct();
    System.out.println("Construct result = " + m.toString());
 
    qexec.close() ; 
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-27, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test14.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test14 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
Construct result = <ModelCom   {u:Amy @u:loves u:Jack; u:John @u:loves u:Jack; u:John @u:loves u:Mary} | >

7.16.11 Test15.java: Query Multiple Models and Specify "Allow Duplicates"

Example 7-28 queries multiple models and uses the "allow duplicates" option. It inserts triples that postulate the following:

• John is a parent of Jack (in Model 1).

• Mary is a parent of Jack (in Model 2).

• Each parent loves all of his or her children.

It then finds out who loves whom. It searches both models and allows for the possibility of duplicate triples in the models (although there are no duplicates in this example).

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
 
public class Test15
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName1 = args[3];
    String szModelName2 = args[4];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model1 = ModelOracleSem.createOracleSemModel(oracle, szModelName1);
    model1.getGraph().add(Triple.create(Node.createURI("u:John"), 
                     Node.createURI("u:parentOf"), Node.createURI("u:Jack")));
    model1.close();
 
    ModelOracleSem model2 = ModelOracleSem.createOracleSemModel(oracle, szModelName2);
    model2.getGraph().add(Triple.create(Node.createURI("u:Mary"), 
                     Node.createURI("u:parentOf"), Node.createURI("u:Jack")));
    model2.close();
 
    String[] modelNamesList = {szModelName2};
    String[] rulebasesList  = {};
    Attachment attachment = Attachment.createInstance(modelNamesList, rulebasesList, 
              InferenceMaintenanceMode.NO_UPDATE,
              QueryOptions.ALLOW_QUERY_VALID_AND_DUP);
 
    GraphOracleSem graph = new GraphOracleSem(oracle, szModelName1, attachment);
    ModelOracleSem model = new ModelOracleSem(graph);
 
    String queryString = " CONSTRUCT { ?s <u:loves> ?o } WHERE {?s <u:parentOf> ?o}";
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
    Model m = qexec.execConstruct();
    System.out.println("Construct result = " + m.toString());
 
    qexec.close() ; 
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName1);
    OracleUtils.dropSemanticModel(oracle, szModelName2);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-28, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test15.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test15 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1 M2
Construct result = <ModelCom   {u:Mary @u:loves u:Jack; u:John @u:loves u:Jack} | >

7.16.12 Test16.java: SPARQL Update

Example 7-29 inserts two triples into a model.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import com.hp.hpl.jena.util.iterator.*;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.update.*;
 
public class Test16
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, szModelName);
    GraphOracleSem g = model.getGraph();
    String insertString =  
      " PREFIX dc: <http://purl.org/dc/elements/1.1/> "         + 
      " INSERT DATA "                                           +
      " { <http://example/book3> dc:title    \"A new book\" ; " +
      "                         dc:creator  \"A.N.Other\" . "   + 
      " }   ";
 
    UpdateAction.parseExecute(insertString,  model);
    ExtendedIterator ei = GraphUtil.findAll(g);
    while (ei.hasNext()) {
      System.out.println("Triple " + ei.next().toString());
    }
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-29, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test16.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test16 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
Triple http://example/book3 @dc:title "A new book"
Triple http://example/book3 @dc:creator "A.N.Other"

7.16.13 Test17.java: SPARQL Query with ARQ Built-In Functions

Example 7-30 inserts data about two books, and it displays the book titles in all uppercase characters and the length of each title string.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import com.hp.hpl.jena.util.iterator.*;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.update.*;
 
public class Test17 {
  public static void main(String[] args) throws Exception  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, szModelName);
    GraphOracleSem g = model.getGraph();
    String insertString =  
      " PREFIX dc: <http://purl.org/dc/elements/1.1/> "         + 
      " INSERT DATA "                                           +
      " { <http://example/book3> dc:title    \"A new book\" ; " +
      "                         dc:creator  \"A.N.Other\" . "   + 
      "   <http://example/book4> dc:title    \"Semantic Web Rocks\" ; " +
      "                         dc:creator  \"TB\" . "   + 
      " }   ";
 
    UpdateAction.parseExecute(insertString,  model);
    String queryString = "PREFIX  dc:   <http://purl.org/dc/elements/1.1/> " +
      " PREFIX  fn: <http://www.w3.org/2005/xpath-functions#> " + 
      " SELECT ?subject (fn:upper-case(?object) as ?object1)  " + 
      "                 (fn:string-length(?object) as ?strlen) " + 
      " WHERE { ?subject dc:title ?object } " 
      ;
    Query query = QueryFactory.create(queryString, Syntax.syntaxARQ);
    QueryExecution qexec = QueryExecutionFactory.create(query, model);
    ResultSet results = qexec.execSelect();
    ResultSetFormatter.out(System.out, results, query);
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-30, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test17.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test17 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
----------------------------------------------------------
| subject                | object1              | strlen |
==========================================================
| <http://example/book3> | "A NEW BOOK"         | 10     |
| <http://example/book4> | "SEMANTIC WEB ROCKS" | 18     |
----------------------------------------------------------

7.16.14 Test18.java: SELECT Cast Query

Example 7-31 "converts" two Fahrenheit temperatures (18.1 and 32.0) to Celsius temperatures.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import com.hp.hpl.jena.util.iterator.*;
import oracle.spatial.rdf.client.jena.*;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.update.*;
 
public class Test18 {
  public static void main(String[] args) throws Exception  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
    
    Oracle oracle = new Oracle(szJdbcURL, szUser, szPasswd);
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, 
szModelName);
    GraphOracleSem g = model.getGraph();
    String insertString =  
      " PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> " +
      " INSERT DATA "                                     +
      " { <u:Object1> <u:temp>    \"18.1\"^^xsd:float ; " +
      "               <u:name>    \"Foo... \" . "         + 
      "   <u:Object2> <u:temp>    \"32.0\"^^xsd:float ; " +
      "               <u:name>    \"Bar... \" . "         + 
      " }   ";
 
    UpdateAction.parseExecute(insertString,  model);
    String queryString = 
      " PREFIX  fn: <http://www.w3.org/2005/xpath-functions#> " + 
      " SELECT ?subject ((?temp - 32.0)*5/9 as ?celsius_temp) " +
      "WHERE { ?subject <u:temp> ?temp } " 
      ;
    Query query = QueryFactory.create(queryString, Syntax.syntaxARQ);
    QueryExecution qexec = QueryExecutionFactory.create(query, model);
    ResultSet results = qexec.execSelect();
    ResultSetFormatter.out(System.out, results, query);
 
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-31, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test18.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test18 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
------------------------------------------------------------------------
| subject     | celsius_temp                                           |
========================================================================
| <u:Object1> | "-7.7222223"^^<http://www.w3.org/2001/XMLSchema#float> |
| <u:Object2> | "0.0"^^<http://www.w3.org/2001/XMLSchema#float>        |
------------------------------------------------------------------------

7.16.15 Test19.java: Instantiate Oracle Database Using OracleConnection

Example 7-32 shows a different way to instantiate an Oracle object using a given OracleConnection object. (In a J2EE Web application, users can normally get an OracleConnection object from a J2EE data source.)

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import com.hp.hpl.jena.util.iterator.*;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.update.*;
import oracle.spatial.rdf.client.jena.*;
import oracle.jdbc.pool.*;
import oracle.jdbc.*;
        
public class Test19 {
  public static void main(String[] args) throws Exception {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
 
    OracleDataSource ds = new OracleDataSource();
    ds.setURL(szJdbcURL);
    ds.setUser(szUser);
    ds.setPassword(szPasswd);
    OracleConnection conn = (OracleConnection) ds.getConnection();
    Oracle oracle = new Oracle(conn);
 
    ModelOracleSem model = ModelOracleSem.createOracleSemModel(oracle, 
szModelName);
    GraphOracleSem g = model.getGraph();
 
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
                        Node.createURI("u:Mary")));
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"),   
                        Node.createURI("u:Jack")));
    g.add(Triple.create(Node.createURI("u:Mary"), Node.createURI("u:parentOf"), 
         Node.createURI("u:Jill")));
    String queryString =
       " SELECT ?s ?o  WHERE { ?s <u:parentOf> ?o .} ";
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
 
    ResultSet results = qexec.execSelect() ;
    ResultSetFormatter.out(System.out, results, query);
    qexec.close() ; 
    model.close();    
    OracleUtils.dropSemanticModel(oracle, szModelName);
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-32, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test19.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test19 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
-----------------------
| s        | o        |
=======================
| <u:John> | <u:Mary> |
| <u:John> | <u:Jack> |
| <u:Mary> | <u:Jill> |
-----------------------

7.16.16 Test20.java: Oracle Database Connection Pooling

Example 7-33 uses Oracle Database connection pooling.

import java.io.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import com.hp.hpl.jena.util.iterator.*;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.update.*;
import oracle.spatial.rdf.client.jena.*;
import oracle.jdbc.pool.*;
import oracle.jdbc.*;
 
public class Test20
{
  public static void main(String[] args) throws Exception
  {
    String szJdbcURL = args[0];
    String szUser    = args[1];
    String szPasswd  = args[2];
    String szModelName = args[3];
 
    // test with connection properties (taken from some example)
    java.util.Properties prop = new java.util.Properties();
    prop.setProperty("MinLimit", "2");     // the cache size is 2 at least 
    prop.setProperty("MaxLimit", "10");
    prop.setProperty("InitialLimit", "2"); // create 2 connections at startup
    prop.setProperty("InactivityTimeout", "1800");    //  seconds
    prop.setProperty("AbandonedConnectionTimeout", "900");  //  seconds
    prop.setProperty("MaxStatementsLimit", "10");
    prop.setProperty("PropertyCheckInterval", "60"); // seconds
 
    System.out.println("Creating OraclePool");
    OraclePool op = new OraclePool(szJdbcURL, szUser, szPasswd, prop, 
               "OracleSemConnPool");
    System.out.println("Done creating OraclePool");
 
    // grab an Oracle and do something with it
    System.out.println("Getting an Oracle from OraclePool");
    Oracle oracle = op.getOracle();
    System.out.println("Done");
    System.out.println("Is logical connection:" +
        oracle.getConnection().isLogicalConnection());
    GraphOracleSem g = new GraphOracleSem(oracle, szModelName);
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
                        Node.createURI("u:Mary")));
    g.close();
    // return the Oracle back to the pool
    oracle.dispose();
    
    // grab another Oracle and do something else 
    System.out.println("Getting an Oracle from OraclePool");
    oracle = op.getOracle();
    System.out.println("Done");
    System.out.println("Is logical connection:" +
        oracle.getConnection().isLogicalConnection());
    g = new GraphOracleSem(oracle, szModelName);
    g.add(Triple.create(Node.createURI("u:John"), Node.createURI("u:parentOf"), 
                        Node.createURI("u:Jack")));
    g.close();
    
    OracleUtils.dropSemanticModel(oracle, szModelName); 
    
    // return the Oracle back to the pool
    oracle.dispose();
  }
}

The following are the commands to compile and run Example 7-33, as well as the expected output of the java command.

javac -classpath jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:log4j-1.2.16.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar Test20.java
java -classpath ./:commons-codec-1.5.jar:httpclient-4.1.2.jar:httpcore-4.1.3.jar:jena-arq-2.9.2.jar:jena-core-2.7.2.jar:jena-iri-0.9.2.jar:jena-tdb-0.9.2.jar:ojdbc6.jar:sdordfclient.jar:sdordf.jar:slf4j-api-1.6.4.jar:slf4j-simple-1.6.4.jar:xercesImpl-2.10.0.jar:xml-apis-1.4.01.jar  Test20 jdbc:oracle:thin:@localhost:1521:orcl scott <password-for-scott> M1
Creating OraclePool
Done creating OraclePool
Getting an Oracle from OraclePool
Done
Is logical connection:true
Getting an Oracle from OraclePool
Done
Is logical connection:true

7.17.1 SPARQL Gateway Features and Benefits Overview

SPARQL Gateway handles several challenges in exposing semantic data to a non-semantic application:

• RDF syntax, SPARQL query syntax and SPARQL protocol must be understood.

• The SPARQL query response syntax must be understood.

• A transformation must convert a SPARQL query response to something that the application can consume.

To address these challenges, SPARQL Gateway manages SPARQL queries and XSLT operations, executes SPARQL queries against any arbitrary standard-compliant SPARQL endpoints, and performs necessary XSL transformations before passing the response back to applications. Applications can then consume semantic data as if it is coming from an existing data source.

Different triple stores or quad stores often have different capabilities. For example, the SPARQL endpoint supported by Oracle Database, with RDF Semantic Graph support for Apache Jena and with Joseki, allows parallel execution, query timeout, dynamic sampling, result cache, and other features, in addition to the core function of parsing and answering a given standard-compliant SPARQL query. However, these features may not be available from another given semantic data store.

With the RDF Semantic Graph SPARQL Gateway, you get certain highly desirable capabilities, such as the ability to set a timeout on a long running query and the ability to get partial results from a complex query in a given amount of time. Waiting indefinitely for a query to finish is a challenge for end users, as is an application with a response time constraint. SPARQL Gateway provides both timeout and best effort query functions on top of a SPARQL endpoint. This effectively removes some uncertainty from consuming semantic data through SPARQL query executions. (See Section 7.17.3.2, "Specifying a Timeout Value" and Section 7.17.3.3, "Specifying Best Effort Query Execution".)

7.17.2 Installing and Configuring SPARQL Gateway

To install and configure SPARQL Gateway, follow these major steps, which are explained in subsections that follow:

1. Download the RDF Semantic Graph Support for Apache Jena .zip File (if Not Already Done)

2. Deploy SPARQL Gateway in WebLogic Server

3. Modify Proxy Settings, if Necessary

4. Configure the OracleSGDS Data Source, if Necessary

5. Add and Configure the SparqlGatewayAdminGroup Group, if Desired

-Dhttp.proxyHost=<your_proxy_host>
-Dhttp.proxyPort=<your_proxy_port>
-Dhttp.nonProxyHosts=127.0.0.1|<hostname_1_for_sparql_endpoint_inside_firewall>|<hostname_2_for_sparql_endpoint_inside_firewall>|...|<hostname_n_for_sparql_endpoint_inside_firewall>

http://<host>:7001/sparqlgateway/admin/sparql.jsp
http://<host>:7001/sparqlgateway/admin/xslt.jsp

7.17.3 Using SPARQL Gateway with Semantic Data

The primary interface for an application to interact with SPARQL Gateway is through a URL with the following format:

http://host:port/sparqlgateway/sg?<SPARQL_ENDPOINT>&<SPARQL_QUERY>&<XSLT>

In the preceding format:

• <SPARQL_ENDPOINT> specifies the ee parameter, which contains a URL encoded form of a SPARQL endpoint.

  For example, ee=http%3A%2F%2Fsparql.org%2Fbooks is the URL encoded string for SPARQL endpoint http://sparql.org/books. It means that SPARQL queries are to be executed against endpoint http://sparql.org/books.

• <SPARQL_QUERY> specifies either the SPARQL query, or the location of the SPARQL query.

  If it is feasible for an application to accept a very long URL, you can encode the whole SPARQL query and set eq=<encoded_SPARQL_query> in the URL If it is not feasible for an application to accept a very long URL, you can store the SPARQL queries and make them available to SPARQL Gateway using one of the approaches described in Section 7.17.3.1.

• <XSLT> specifies either the XSL transformation, or the location of the XSL transformation.

  If it is feasible for an application to accept a very long URL, you can encode the whole XSL transformation and set ex=<encoded_XSLT> in the URL If it is not feasible for an application to accept a very long URL, you can store the XSL transformations and make them available to SPARQL Gateway using one of the approaches described in Section 7.17.3.1.

Related topics:

• Storing SPARQL Queries and XSL Transformations

• Specifying a Timeout Value

• Specifying Best Effort Query Execution

• Specifying a Content Type Other Than text/xml

http://host:port/sparqlgateway/sg?<SPARQL_ENDPOINT>&<SPARQL_QUERY>&<XSLT>&t=1000

http://host:port/sparqlgateway/sg?<SPARQL_ENDPOINT>&<SPARQL_QUERY>&<XSLT>&t=1000&b=t

<init-param>
  <param-name>sparql_gateway_besteffort_maxrounds</param-name>
  <param-value>10</param-value>
</init-param>
 
<init-param>
  <param-name>sparql_gateway_besteffort_maxthreads</param-name>
  <param-value>3</param-value>
</init-param>

http://host:port/sparqlgateway/sg?<SPARQL_ENDPOINT>&<SPARQL_QUERY>&<XSLT>&rt=<content_type>

7.17.4 Customizing the Default XSLT File

You can customize the default XSL transformation file (the one referenced using wx=default.xslt). This section presents some examples of customizations.

The following example implements this namespace prefix replacement logic: if a variable binding returns a URI that starts with http://purl.org/goodrelations/v1#, that portion is replaced by gr:; and if a variable binding returns a URI that starts with http://www.w3.org/2000/01/rdf-schema#, that portion is replaced by rdfs:.

<xsl:when test="starts-with(text(),'http://purl.org/goodrelations/v1#')">
   <xsl:value-of select="concat('gr:',substring-after(text(),'http://purl.org/goodrelations/v1#'))"/>
</xsl:when>
...
<xsl:when test="starts-with(text(),'http://www.w3.org/2000/01/rdf-schema#')">
   <xsl:value-of select="concat('rdfs:',substring-after(text(),'http://www.w3.org/2000/01/rdf-schema#'))"/>
</xsl:when>

The following example implements logic to trim a leading http://localhost/ or a leading http://127.0.0.1/.

<xsl:when test="starts-with(text(),'http://localhost/')">
  <xsl:value-of select="substring-after(text(),'http://localhost/')"/>
</xsl:when>
<xsl:when test="starts-with(text(),'http://127.0.0.1/')">
  <xsl:value-of select="substring-after(text(),'http://127.0.0.1/')"/>
</xsl:when>

7.17.5 Using the SPARQL Gateway Java API

In addition to a Web interface, the SPARQL Gateway administration service provides a convenient Java application programming interface (API) for managing SPARQL queries and their associated XSL transformations. The Java API is included in the RDF Semantic Graph support for Apache Jena library, sdordfclient.jar.

Java API reference information is available in the javadoc_sparqlgateway.zip file that is included in the SPARQL Gateway .zip file (described in Section 7.17.2.1).

The main entry point for this API is the oracle.spatial.rdf.client.jena.SGDBHandler class (SPARQL Gateway Database Handler), which provides the following static methods for managing queries and transformations:

• deleteSparqlQuery(Connection, int)

• deleteXslt(Connection, int)

• insertSparqlQuery(Connection, int, String, String, boolean)

• insertXslt(Connection, int, String, String, boolean)

• getSparqlQuery(Connection, int, StringBuilder, StringBuilder)

• getXslt(Connection, int, StringBuilder, StringBuilder)

These methods manipulate and retrieve entries in the SPARQL Gateway associated tables that are stored in an Oracle Database instance. To use these methods, the necessary associated tables must already exist. If the tables do not exist, deploy the SPARQL Gateway on a Web server and access a URL in the following format:

http://<host>:<port>/sparqlgateway/sg?

where <host> is the host name of the Web server and <port> is the listening port of the Web server. Accessing this URL will automatically create the necessary tables if they do not already exist.

Any changes made through the Java API affect the SPARQL Gateway Web service in the same way as changes made through the administration Web interface. This provides the flexibility to manage queries and transformations using the interface you find most convenient.

Note that the insert methods provided by the Java API will not replace existing queries or transformations stored in the tables. Attempting to replace an existing query or transformation will fail. To replace a query or transformation, you must remove the existing entry in the table using one of the delete methods, and then insert the new query or transformation using one of the insert methods.

The following examples demonstrate how to perform common management tasks using the Java API. The examples assume a connection has already been established to the underlying Oracle Database instance backing the SPARQL Gateway.

Example 7-34 adds a query and an XSL transformation to the database backing the SPARQL Gateway. After the query and transformation are added, other programs can use the query and transformation through the gateway by specifying the appropriate query ID (qid) and XSL transformation ID (xid) in the request URL.

String query = "PREFIX ... SELECT ..."; // full SPARQL query text
String xslt  = "<?xml ...> ...";        // full XSLT transformation text
 
String queryDesc = "Conference attendee information"; // description of SPARQL query
String xsltDesc = "BIEE table widget transformation"; // description of XSLT transformation
 
int queryId = queryIdCounter++; // assign a unique ID to this query
int xsltId  = xsltIdCounter++;  // assign a unique ID to this transformation
 
// Inserting a query or transformation will fail if the table already contains
// an entry with the same ID.  Setting this boolean to true will ignore these
// exceptions (but the table will remain unchanged). Here we specify that we
// want an exception thrown if we encounter a duplicate ID.
boolean ignoreDupException = false;
 
// add the query
try {
  // Delete query if one already exists with this ID (this will not throw an
  // error if no such entry exists)
  SGDBHandler.deleteSparqlQuery( connection, queryId );
  SGDBHandler.insertSparqlQuery( connection, queryId, query, queryDesc, ignoreDupException );
} catch( SQLException sqle ) {
  // Handle exception
} catch( QueryException qe ) {
  // Handle query syntax exception
}
 
// add the XSLT
try {
  // Delete xslt if one already exists with this ID (this will not throw an
  // error if no such entry exists)
  SGDBHandler.deleteXslt( connection, xsltId );
  SGDBHandler.insertXslt( connection, xsltId, xslt, xsltDesc, ignoreDupException );
}  catch( SQLException sqle ) {
  // Handle database exception
} catch( TransformerConfigurationException tce ) {
  // Handle XSLT syntax exception
}

Example 7-35 retrieves an existing query from the database, modifies it, then stores the updated version of the query back in the database. These steps simulate editing a query and saving the changes. (Note that if the query does not exist, an exception is thrown.)

StringBuilder query;
StringBuilder description;
 
// Populate these with the query text and description from the database
query = new StringBuilder( );
description = new StringBuilder( );
 
// Get the query from the database
try {
  SGDBHandler.getSparqlQuery( connection, queryId, query, description );
} catch( SQLException sqle ) {
  // Handle exception
  // NOTE: exception is thrown if query with specified ID does not exist
}
 
// The query and description should be populated now
 
// Modify the query 
String updatedQuery = query.toString( ).replaceAll("invite", "attendee");
 
// Insert the query back into the database
boolean ignoreDup = false;
try {
  // First must delete the old query
  SGDBHandler.deleteSparqlQuery( connection, queryId );
  // Now we can add
  SGDBHandler.insertSparqlQuery( connection, queryId, updatedQuery, description.toString( ), ignoreDup );
} catch( SQLException sqle ) {
  // Handle exception
} catch( QueryException qe ) {
  // Handle query syntax exception
}

Example 7-36 retrieves an existing XSL transformation and prints it to standard output. (Note that if the transformation does not exist, an exception is thrown.)

StringBuilder xslt;
StringBuilder description;
 
// Populate these with the XSLT text and description from the database
xslt = new StringBuilder( );
description = new StringBuilder( );
 
try {
  SGDBHandler.getXslt( connection, xsltId, xslt, description );
} catch( SQLException sqle ) {
  // Handle exception
  // NOTE: exception is thrown if transformation with specified ID does not exist
}
 
// Print it to standard output
System.out.printf( "XSLT description: %s\n", description.toString( ) );
System.out.printf( "XSLT body:\n%s\n", xslt.toString( ) );

7.17.6 Using the SPARQL Gateway Graphical Web Interface

SPARQL Gateway provides several browser-based interfaces to help you test queries, navigate semantic data, and manage SPQARQL query and XSLT files:

• Main Page (index.html)

• Navigation and Browsing Page (browse.jsp)

• XSLT Management Page (xslt.jsp)

• SPARQL Management Page (sparql.jsp)

7.17.6.1 Main Page (index.html)

http://<host>:<port>/sparqlgateway/index.html provides a simple interface for executing SPARQL queries and then applying the transformations in the default.xslt file to the response. Figure 7-2 shows this interface for executing a query.

Figure 7-2 Graphical Interface Main Page (index.html)

Description of "Figure 7-2 Graphical Interface Main Page (index.html)"

Enter or select a SPARQL Endpoint, specify the SPARQL SELECT Query Body, and press Submit Query.

For example, if you specify http://dbpedia.org/sparql as the SPARQL endpoint and use the SPARQL query body from Figure 7-2, the response will be similar to Figure 7-3. Note that the default transformations (in default.xslt) have been applied to the XML output in this figure.

Figure 7-3 SPARQL Query Main Page Response

Description of "Figure 7-3 SPARQL Query Main Page Response"

7.17.6.2 Navigation and Browsing Page (browse.jsp)

http://<host>:<port>/sparqlgateway/browse.jsp provides navigation and browsing capabilities for semantic data. It works against any standard compliant SPARQL endpoint. Figure 7-4 shows this interface for executing a query.

Figure 7-4 Graphical Interface Navigation and Browsing Page (browse.jsp)

Description of "Figure 7-4 Graphical Interface Navigation and Browsing Page (browse.jsp)"

Enter or select a SPARQL Endpoint, specify the SPARQL SELECT Query Body, optionally specify a Timeout (ms) value in milliseconds and the Best Effort option, and press Submit Query.

The SPARQL response is parsed and then presented in table form, as shown in Figure 7-5.

Figure 7-5 Browsing and Navigation Page: Response

Description of "Figure 7-5 Browsing and Navigation Page: Response"

In Figure 7-5, note that URIs are clickable to allow navigation, and that when users move the cursor over a URI, tool tips are shown for the URIs which have been shortened for readability (as in http://purl.org.dc/elements/1.1/title being displayed as the tool tip for dc:title in the figure).

If you click the URI http://example.org/book/book5 in the output shown in Figure 7-5, a new SPARQL query is automatically generated and executed. This generated SPARQL query has three query patterns that use this particular URI as subject, predicate, and object, as shown in Figure 7-6. Such a query can give you a good idea about how this URI is used and how it is related to other resources in the data set.

Figure 7-6 Query and Response from Clicking URI Link

Description of "Figure 7-6 Query and Response from Clicking URI Link"

When there are many matches of a query, the results are organized in pages and you can click on any page. The page size by default is 50 results. To display more (or fewer) than 50 rows per page in a response with the Browsing and Navigation Page (browse.jsp), you can specify the &resultsPerPage parameter in the URL. For example, to allow 100 rows per page, include the following in the URL:

&resultsPerPage=100

7.17.6.3 XSLT Management Page (xslt.jsp)

http://<host>:<port>/sparqlgateway/admin/xslt.jsp provides a simple XSLT management interface. You can enter an XSLT ID (integer) and click Get XSLT to retrieve both the Description and XSLT Body. You can modify the XSLT Body text and then save the changes by clicking Save XSLT. Note that there is a previewer to help you navigate among available XSLT definitions.

Figure 7-7 shows the XSLT Management Page.

Figure 7-7 XSLT Management Page

Description of "Figure 7-7 XSLT Management Page"

7.17.6.4 SPARQL Management Page (sparql.jsp)

http://<host>:<port>/sparqlgateway/admin/xslt.jsp provides a simple SPARQL management interface. You can enter a SPARQL ID (integer) and click Get SPARQL to retrieve both the Description and SPARQL Body. You can modify the SPARQL Body text and then save the changes by clicking Save SPARQL. Note that there is a previewer to help you navigate among available SPARQL queries.

Figure 7-8 shows the SPARQL Management Page.

Figure 7-8 SPARQL Management Page

Description of "Figure 7-8 SPARQL Management Page"

7.17.7 Using SPARQL Gateway as an XML Data Source to OBIEE

This section explains how to create an XML Data source for Oracle Business Intelligence Enterprise Edition (OBIEE), by integrating OBIEE with RDF using SPARQL Gateway as a bridge. (The specific steps and illustrations reflect the Oracle BI Administration Tool Version 11.1.1.3.0.100806.0408.000.)

1. Start the Oracle BI Administration Tool.

2. Click File, then Import Metadata. The first page of the Import Metadata wizard is displayed, as shown in Figure 7-9.

   Figure 7-9 Import Metadata - Select Data Source

   
   Description of "Figure 7-9 Import Metadata - Select Data Source"
   
   

   Connection Type: Select XML.

   URL: URL for an application to interact with SPARQL Gateway, as explained in Section 7.17.3. You can also include the timeout and best effort options.

   Ignore the User Name and Password fields.

3. Click Next. The second page of the Import Metadata wizard is displayed, as shown in Figure 7-10.

   Figure 7-10 Import Metadata - Select Metadata Types

   
   Description of "Figure 7-10 Import Metadata - Select Metadata Types"
   
   

   Select the desired metadata types to be imported. Be sure that Tables is included in the selected types.

4. Click Next. The third page of the Import Metadata wizard is displayed, as shown in Figure 7-11.

   Figure 7-11 Import Metadata - Select Metadata Objects

   
   Description of "Figure 7-11 Import Metadata - Select Metadata Objects"
   
   

   In the Data Source View, expand the node that has the table icon, select the column names (mapped from projected variables defined in the SPARQL SELECT statement), and click the right-arrow (>) button to move the selected columns to the Repository View.

5. Click Finish.

6. Complete the remaining steps for the usual BI Business Model work and Mapping and Presentation definition work, which are not specific to SPARQL Gateway or RDF data.

7.18.1 Deploying Joseki in Apache Tomcat 6.0.29 or 7.0.42

To deploy Joseki in Apache Tomcat 6.0.29 or 7.0.42, follow these steps.

1. Download and install Apache Tomcat 6.0.29 or 7.0.42.

   The directory root for Apache Tomcat installation will be referred to in these instructions as $CATALINA_HOME.

2. Set up environment variables using the following as examples:

   setenv JAVA_HOME< your_path_here>/jdk16/
   setenv PATH <your_path_here>/jdk16/bin/:$PATH 
   setenv CATALINA_HOME <your_path_here>/apache-tomcat-6.0.29 OR
   setenv CATALINA_HOME <your_path_here>/apache-tomcat-7.0.42
   

3. Copy ojdbc6.jar into ${CATALINA_HOME}/lib.

4. Modify tomcat-users.xml so that it includes the following:

   <tomcat-users> 
   <role rolename="tomcat"/> 
   <role rolename="role1"/> 
   <user username="tomcat" password="<tomcat-password>" roles="tomcat,manager"/> 
   <user username="both" password="<tomcat-password>" roles="tomcat,role1"/> 
   <user username="role1" password="<tomcat-password>" roles="role1"/> 
   </tomcat-users>
   

   However, if you are using Apache Tomcat version 7.0.42, replace roles="tomcat,manager" with roles="tomcat,manager-gui" in the preceding code.

5. Start Tomcat:

   $CATALINA_HOME/bin/startup.sh
   

   If this file does not have executable permission, enter the following command and then again attempt to start Tomcat:

   chmod u+x $CATALINA_HOME/bin/startup.sh
   

6. In a browser go to: http://hostname:8080/manager/html

   If authentication is required, enter tomcat for the user and then enter the Tomcat password.

7. Deploy Joseki in Tomcat.

   1. In the Tomcat Manager page (http://hostname:8080/manager/html), select Deploy directory or WAR file located on server.

   2. For Context Path, enter: /joseki

   3. For WAR or Directory URL, enter the path to joseki.war, for example: /tmp/jena_adapter/joseki_web_app/joseki.war

   4. Click Deploy.

   A directory named joseki has been created under apache-tomcat-6.0.29/webapps or apache-tomcat-7.0.42/webapps. This directory will be referred to as JOSEKI_HOME.

8. Verify that Joseki is installed properly by going to:

   http://<hostname>:8080/joseki
   

9. Create a J2EE data source named OracleSemDS.

   During the data source creation, you can specify a user and password for the database schema that contains the relevant semantic data against which SPARQL queries are to be executed. To create a data source in Tomcat, make the following changes:

   • In the global $CATALINA_HOME/conf/server.xml file, add the following resource in GlobalNamingResources (customize where needed):

     <Resource name="OracleSemDS" auth="Container" type="oracle.jdbc.pool.OracleDataSource" driverClassName="oracle.jdbc.OracleDriver" factory="oracle.jdbc.pool.OracleDataSourceFactory" url="jdbc:oracle:thin:@hostname:port:sid" user="username" password="password" maxActive="30" maxIdle="10" maxWait="-1"/>
     

   • In the global $CATALINA_HOME/conf/context.xml file, add the following link:

     <ResourceLink global="OracleSemDS" name="OracleSemDS" type="oracle.jdbc.pool.OracleDataSource"/>
     

   For more information about setting up data sources, see the Tomcat documentation.

10. Shut down and restart Tomcat:

    $CATALINA_HOME/bin/shutdown.sh 
    $CATALINA_HOME/bin/startup.sh
    

11. Verify your deployment by going to (assuming that the web application is deployed at port 8080):

    http://<hostname>:8080/joseki/querymgt?abortqid=0
    

    You should see an XML response, which indicates a successful deployment of Joseki with the RDF Semantic Graph support for Apache Jena query management servlet.

7.18.2 Deploying Joseki in JBoss 7.1.1

To deploy Joseki in JBoss 7.1.1, follow these steps. (The steps have also been tested, with modifications as needed, against Red Hat JBoss Enterprise Application Platform 6.1.0.)

1. Download and install JBoss Application Server 7.1.1.

   These instructions assume that jboss-as-7.1.1.Final/ is the top-level directory of the JBoss installation.

2. Install the JDBC driver:

   create directory jboss-as-7.1.1.Final/modules/oracle/jdbc/main/
   

3. Copy ojdbc6.jar into this directory

4. Create module.xml in this directory with the following content:

   <?xml version="1.0" encoding="UTF-8"?>
    <module xmlns="urn:jboss:module:1.0" name="oracle.jdbc">
        <resources>
           <resource-root path="ojdbc6.jar"/>
       </resources>
       <dependencies>
           <module name="javax.api"/>
            <module name="javax.transaction.api"/>
        </dependencies>
   </module>
   

5. Modify jboss-as-7.1.1.Final/standalone/configuration/standalone.xml by adding the following line:

   <driver name="OracleJDBCDriver" module="oracle.jdbc"/>
   

   The modified standalone.xml file should include the following:

   ...
          <drivers>
            <driver name="OracleJDBCDriver" module="oracle.jdbc"/>
            <driver name="h2" module="com.h2database.h2">
                 <xa-datasource-class>org.h2.jdbcx.JdbcDataSource</xa-datasource-class>
             </driver>
          </drivers>
   ...
   

6. Create the necessary data source.

   1. Log into the JBoss AS Administration Console:

      http://<hostname>:9990/console/App.html#server-overview
      

   2. Click Datasource.

   3. Click Profile.

   4. Click Add, and enter the following:

      Name: OracleSemDS

      JNDI Name: java:jboss/datasources/OracleSemDS

   5. Select OracleJDBCDriver.

   6. Click Next.

      The following information is displayed:

      Connection URL: jdbc:oracle:thin:@hostname:port:sid     NOTE: customize
      Username:    scott                                       NOTE: customize
      Password:    tiger                                       NOTE: customize
      Security Domain: (Leave empty)
      

   7. Customize the information as needed and leave Security Domain blank, and click Done.

7. Highlight this new data source, click Enable, then click Confirm.

8. Deploy the joseki.war file using the JBoss Administration Console.

   1. Go to the following page:

      http://<hostname>:9990/console/App.html#deployments
      

   2. Click Deployments.

   3. Click Manage Deployments.

   4. Click Add and specify the joseki.war file.