Augmenting the Knowledge Base with a Custom Thesaurus

14.5 Augmenting the Knowledge Base with a Custom Thesaurus

You can add your custom thesaurus to a branch in the existing knowledge base. The knowledge base is a hierarchical tree of concepts used for theme indexing, ABOUT queries, and derived themes for document services.

When you augment the existing knowledge base with your new thesaurus, you query with the ABOUT operator. The query implicitly expands to synonyms and narrower terms. You do not query with the thesaurus operators.

To augment the existing knowledge base with your custom thesaurus:

Create your custom thesaurus, linking new terms to existing knowledge base terms.
Load the thesaurus one of the following ways:
- Using the ctxload utility. See "Example of Loading a Thesaurus with ctxload".
- Using the PL/SQL procedure CTX_THES.IMPORT_THESAURUS. See "Example of Loading a Thesaurus with the CTX_THES.IMPORT_THESAURUS PL/SQL procedure".
Compile the loaded thesaurus with the ctxkbtc compiler.
Index your documents. By default the system creates a theme component for your index.
Use the ABOUT operator to query. For example, to find all documents that are related to the term politics, including any synonyms or narrower terms as defined in the knowledge base, enter this query:
```
'about(politics)'
```
See Also:
- "Defining Terms in a Thesaurus" and "Linking New Terms to Existing Terms"
- "Compiling a Loaded Thesaurus"

14.5.1 Advantages

Compiling your custom thesaurus with the existing knowledge base before indexing enables faster and simpler queries with the ABOUT operator. Document services can also take full advantage of the customized information to create theme summaries and gists.

14.5.2 Limitations

Use of the ABOUT operator requires a theme component in the index, which requires slightly more disk space. You must also define the thesaurus before indexing your documents. If you change the thesaurus, you must recompile your thesaurus and reindex your documents.