A stopword is a word that is not to be indexed. A stopword is usually a low information word such as this or that in English.
The system supplies a list of stopwords called a stoplist for every language. By default during indexing, the system uses the Oracle Text default stoplist for your language.
You can edit the default stoplist CTXSYS.DEFAULT_STOPLIST or create your own with the following PL/SQL procedures:
CTX_DDL.CREATE_STOPLIST
CTX_DDL.ADD_STOPWORD
CTX_DDL.REMOVE_STOPWORD
You specify your custom stoplists in the parameter clause of CREATE INDEX.
You can also dynamically add stopwords after indexing with the ALTER INDEX statement.
You can create multi-language stoplists to hold language-specific stopwords. A multi-language stoplist is useful when you use the MULTI_LEXER to index a table that contains documents in different languages, such as English, German, and Japanese.
To create a multi-language stoplist, use the CTX_DDL.CREATE_STOPLIST procedure and specify a stoplist type of MULTI_STOPLIST. You add language specific stopwords with CTX_DDL.ADD_STOPWORD.
In addition to defining your own stopwords, you can define stopthemes, which are themes that are not to be indexed. This feature is available for English and French only.
You can also specify that numbers are not to be indexed. A class of alphanumeric characters such a numbers that is not to be indexed is a stopclass.
You record your own stopwords, stopthemes, stopclasses by creating a single stoplist, to which you add the stopwords, stopthemes, and stopclasses. You specify the stoplist in the paramstring for CREATE INDEX.
You use the following procedures to manage stoplists, stopwords, stopthemes, and stopclasses:
CTX_DDL.CREATE_STOPLIST
CTX_DDL.ADD_STOPWORD
CTX_DDL.ADD_STOPTHEME
CTX_DDL.ADD_STOPCLASS
CTX_DDL.REMOVE_STOPWORD
CTX_DDL.REMOVE_STOPTHEME
CTX_DDL.REMOVE_STOPCLASS
CTX_DDL.DROP_STOPLIST
Oracle Text Reference to learn more about using these statements