Stemming User-Dictionaries

You can create a user-dictionary for your own language to customize how words are decomposed.

Table 20 Stemming User-Dictionaries

Dictionary	Stemmer
$ORACLE_HOME/ctx/data/frlx/drfr.dct	French
$ORACLE_HOME/ctx/data/delx/drde.dct	German
$ORACLE_HOME/ctx/data/nllx/drnl.dct	Dutch
$ORACLE_HOME/ctx/data/itlx/drit.dct	Italian
$ORACLE_HOME/ctx/data/eslx/dres.dct	Spanish
$ORACLE_HOME/ctx/data/enlx/dren.dct	English and Derivational

Stemming user-dictionaries are not supported for languages other than those listed in Table 2-20.

The format for the user dictionary is as follows:

output term <tab> input term

The individual parts of the decomposed word must be separated by the # character. The following example entries are for the German word Hauptbahnhof:

Hauptbahnhof<tab>Haupt#Bahnhof
Hauptbahnhofes<tab>Haupt#Bahnhof
Hauptbahnhof<tab>Haupt#Bahnhof
Hauptbahnhoefe<tab>Haupt#Bahnhof

index_themes

Specify YES to index theme information in English or French. This makes ABOUT queries more precise. The index_themes and index_text attributes cannot both be NO. The default is NO.

You can set this parameter to TRUE for any index type. To enter an ABOUT query with CATSEARCH, use the query template with CONTEXT grammar.

prove_themes

Specify YES to prove themes. Theme proving attempts to find related themes in a document. When no related themes are found, parent themes are eliminated from the document.

While theme proving is acceptable for large documents, short text descriptions with a few words rarely prove parent themes, resulting in poor recall performance with ABOUT queries.

Theme proving results in higher precision and less recall (less rows returned) for ABOUT queries. For higher recall in ABOUT queries and possibly less precision, you can disable theme proving. Default is YES.

The prove_themes attribute is supported for CONTEXT and CTXRULE indexes.

theme_language

Specify which knowledge base to use for theme generation when index_themes is set to YES. When index_themes is NO, setting this parameter has no effect on anything.

Specify any globalization support language or AUTO. You must have a knowledge base for the language you specify. This release provides a knowledge base in only English and French. In other languages, you can create your own knowledge base.

See Also: “Adding a Language-Specific Knowledge Base” in Oracle Text Utilities.

The default is AUTO, which instructs the system to set this parameter according to the language of the environment.

index_stems

Specify the stemmer to use for stem indexing. Choose one of the following stemmers:

NONE, Arabic, Bokmal (Norwegian), Catalan, Croatian, Czech, Danish, Derivational, Dutch, English, Finnish, French, German, Hebrew, Hungarian, Italian, Nynorsk (Norwegian), Polish, Portuguese, Romanian, Slovak, Slovenian, Spanish, and Swedish

Tokens are stemmed to a single base form at index time in addition to the normal forms. Indexing stems enables better query performance for stem ($) queries, such as $computed.

Note: If the index_stems attribute is set to one of the languages with ID 8 to 33, which are listed Table 2-19, then the stemmer attribute of BASIC_WORDLIST will be ignored and the stemmer used by the BASIC_LEXER will be used during query to determine the stem of the given query term.

index_text

Specify YES to index word information. The index_themes and index_text attributes cannot both be NO.

The default is YES.

alternate_spelling

Specify either German, Danish, or Swedish to enable the alternate spelling in one of these languages. Enabling alternate spelling enables you to query a word in any of its alternate forms.

Alternate spelling is off by default; however, in the language-specific scripts that Oracle provides in admin/defaults (drdefd.sql for German, drdefdk.sql for Danish, and drdefs.sql for Swedish), alternate spelling is turned on. If your installation uses these scripts, then alternate spelling is on. However, you can specify NONE for no alternate spelling. For more information about the alternate spelling conventions Oracle Text uses, see Alternate Spelling.

new_german_spelling

Specify whether the queries using the BASIC_LEXER return both traditional and reformed (new) spellings of German words. If new_german_spelling is set to YES, then both traditional and new forms of words are indexed. If it is set to NO, then the word will be indexed only as it as provided in the query. The default is NO.

See Also: “New German Spelling”