Last updated on MARCH 19, 2015
Applies to:Oracle Text - Version 220.127.116.11 to 18.104.22.168 [Release 9.2 to 12.1]
Information in this document applies to any platform.
This article is meant to discuss how the knowledge base in Oracle Text can be extended, or one created for languages where none is supplied. It also attempts to dispel the confusion that can sometimes arise between the knowledge base and the concept of a default thesaurus.
The knowledge base is the information source Oracle Text uses to perform theme analysis. This is used in theme indexing, processing ABOUT queries and document theme extraction with the CTX_DOC package. A knowledge base is supplied for English and French but not, currently, for any other language.
The information in the knowledge base is organised in the same way as in a thesaurus, therefore it can be extended by compiling one or more thesauri with the information already present. There is no facility for removing, exporting (dumping) or replacing the supplied knowledge base, but for languages other than English or French, the extension will create a new, user-defined knowledge base for that language (there is only ever one knowledge base only per installation).
The utility to extend the existing knowledge base, or create a new, language-specific knowledge base, is the Knowledge Base Extension Compiler (ctxkbtc).
- The thesaurus used is first added to the database using the ctxload executable.
- The knowledge base is then extended using the information in the thesaurus using the ctxkbtc executable
- See the Oracle Text Reference, Chapter "Oracle Text Utilities", for syntax and examples.
- Also see ' Extending the Knowledge Base' in the Oracle Technology Network (OTN), at:
Although the knowledge base can be created or extended using a thesaurus file, its functionality should not be confused with the thesaurus functionality provided by the CTX_THES package. When using the CTX_THES operators there is the concept of a DEFAULT thesaurus, that is the one used when no specific thesaurus is defined. However no such thesaurus is provided. If required a thesaurus can be created with the name 'DEFAULT' and will be used for this purpose.
Creating a DEFAULT thesaurus, however, will not affect the knowledge base in any way, not will extensions to the knowledge base affect this thesaurus in any way. They are quite different entities, and are used for entirely different purposes.
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