About the Supplied Knowledge Base

Oracle Text supplies a knowledge base for English and French. The supplied knowledge contains the information used to perform theme analysis. Theme analysis includes theme indexing, ABOUT queries, and theme extraction with the CTX_DOC package.

The knowledge base is a hierarchical tree of concepts and categories. It has six main branches:

• science and technology

• business and economics

• government and military

• social environment

• geography

• abstract ideas and concepts

  See Also: Oracle Text Reference for the breakdown of the category hierarchy.

The supplied knowledge base is like a thesaurus in that it is hierarchical and contains broader term, narrower term, and related term information. As such, you can improve the accuracy of theme analysis by augmenting the knowledge base with your industry-specific thesaurus by linking new terms to existing terms.

See Also: "Augmenting Knowledge Base with Custom Thesaurus" in this chapter.

You can also extend theme functionality to other languages by compiling a language-specific thesuarus into a knowledge base.

See Also: "Adding a Language-Specific Knowledge Base" in this chapter.

Knowledge Base Character Set

Knowledge bases can be in any single-byte character set. Supplied knowledge bases are in WE8ISO8859P1. You can store an extended knowledge base in another character set such as US7ASCII.

Adding a Language-Specific Knowledge Base

You can extend theme functionality to languages other than English or French by loading your own knowledge base for any single-byte whitespace delimited language, including Spanish.

Theme functionality includes theme indexing, ABOUT queries, theme highlighting, and the generation of themes, gists, and theme summaries with CTX_DOC.

You extend theme functionality by adding a user-defined knowledge base. For example, you can create a Spanish knowledge base from a Spanish thesuarus.

To load your language-specific knowledge base, follow these steps:

1. Load your custom thesaurus using ctxload.

2. Set NLS_LANG so that the language portion is the target language. The charset portion must be a single-byte character set.

3. Compile the loaded thesaurus using ctxkbtc:

ctxkbtc -user ctxsys/ctxsys -name my_lang_thes

This command compiles your language-specific knowledge base from the loaded thesaurus. To use this knowledge base for theme analysis during indexing and ABOUT queries, specify the NLS_LANG language as the THEME_LANGUAGE attribute value for the BASIC_LEXER preference.

Limitations

The following limitations hold for adding knowledge bases:

• Oracle supplies knowledge bases in English and French only. You must provide your own thesaurus for any other language.

• You can only add knowledge bases for languages with single-byte character sets. You cannot create a knowledge base for languages which can be expressed only in multi-byte character sets. If the database is a multi-byte universal character set, such as UTF-8, the NLS_LANG parameter must still be set to a compatible single-byte character set when compiling the thesaurus.

• Adding a knowledge base works best for whitespace delimited languages.

• You can have at most one knowledge base per NLS language.

• Obtaining hierarchical query feedback information such as broader terms, narrower terms and related terms does not work in languages other than English and French. In other languages, the knowledge bases are derived entirely from your thesauri. In such cases, Oracle recommends that you obtain hierarchical information directly from your thesauri.

  See Also: Oracle Text Reference for more information about theme indexing, ABOUT queries, using the CTX_DOC package, and the supplied English knowledge base.