ABOUT

Use the ABOUT operator to return documents that are related to a query term or phrase.

General Behavior

In English and French, ABOUT enables you to query on concepts, even if a concept is not actually part of a query. For example, an ABOUT query on heat might return documents related to temperature, even though the term temperature is not part of the query.

In other languages, using ABOUT will often increase the number of returned documents and may improve the sorting order of results. For all languages, Oracle Text scores results for an ABOUT query with the most relevant document receiving the highest score.

English and French Behavior

In English and French, use the ABOUT operator to query on concepts. The system looks up concept information in the theme component of the index. Create a theme component to your index by setting the INDEX_THEMES BASIC_LEXER attribute to YES.

Note: You need not have a theme component in the index to enter ABOUT queries in English and French. However, having a theme component in the index yields the best results for ABOUT queries.

Oracle Text retrieves documents that contain concepts that are related to your query word or phrase. For example, if you enter an ABOUT query on California, the system might return documents that contain the terms Los Angeles and San Francisco, which are cities in California.The document need not contain the term California to be returned in this ABOUT query.

The word or phrase specified in your ABOUT query need not exactly match the themes stored in the index. Oracle Text normalizes the word or phrase before performing lookup in the index.

You can use the ABOUT operator with the CONTAINS and CATSEARCH SQL operators. In the case of CATSEARCH, you must use query templating with the CONTEXT grammar to query on the indexed themes. See ABOUT Query with CATSEARCH in the Examples section.

Syntax

Syntax Description

Syntax	Description
about(phrase)	In all languages, increases the number of relevant documents returned for the same query without the `ABOUT` operator. The phrase parameter can be a single word or a phrase, or a string of words in free text format. In English and French, returns documents that contain concepts related to phrase, provided the `BASIC_LEXER` `INDEX_THEMES` attribute is set to YES at index time. The score returned is a relevance score. Oracle Text ignores any query operators that are included in phrase. If your index contains only theme information, an `ABOUT` operator and operand must be included in your query on the text column or else Oracle Text returns an error. The phrase you specify cannot be more than 4000 characters.

about(phrase)

In all languages, increases the number of relevant documents returned for the same query without the ABOUT operator. The phrase parameter can be a single word or a phrase, or a string of words in free text format.

In English and French, returns documents that contain concepts related to phrase, provided the BASIC_LEXER INDEX_THEMES attribute is set to YES at index time.

The score returned is a relevance score.

Oracle Text ignores any query operators that are included in phrase.

If your index contains only theme information, an ABOUT operator and operand must be included in your query on the text column or else Oracle Text returns an error.

The phrase you specify cannot be more than 4000 characters.

Case-Sensitivity

ABOUT queries give the best results when your query is formulated with proper case. This is because the normalization of your query is based on the knowledge catalog which is case-sensitive.

However, you need not type your query in exact case to obtain results from an ABOUT query. The system does its best to interpret your query. For example, if you enter a query of CISCO and the system does not find this in the knowledge catalog, the system might use Cisco as a related concept for look-up.

Improving ABOUT Results

The ABOUT operator uses the supplied knowledge base in English and French to interpret the phrase you enter. Your ABOUT query therefore is limited to knowing and interpreting the concepts in the knowledge base.

Improve the results of your ABOUT queries by adding your application-specific terminology to the knowledge base.

See Also: “Extending the Knowledge Base” in Oracle Text Utilities

Limitations

The phrase you specify in an ABOUT query cannot be more than 4000 characters.
The ABOUT query operator is not supported within sections.
The JSON_TEXTCONTAINS query does not support the ABOUT operator.

Examples for ABOUT Operator

Single Words

To search for documents that are about soccer, use the following syntax:

'about(soccer)'

Phrases

Further refine the query to include documents about soccer rules in international competition by entering the phrase as the query term:

'about(soccer rules in international competition)'

In this English example, Oracle Text returns all documents that have themes of soccer, rules, or international competition.

In terms of scoring, documents which have all three themes will generally score higher than documents that have only one or two of the themes.

Unstructured Phrases

You can also query on unstructured phrases, such as the following:

'about(japanese banking investments in indonesia)'

Combined Queries

Use other operators, such as AND or NOT, to combine ABOUT queries with word queries. For example, enter the following combined ABOUT and word query:

'about(dogs) and cat'

Combine an ABOUT query with another ABOUT query as follows:

'about(dogs) not about(labradors)'

Note: You cannot combine ABOUT with the WITHIN operator, as for example ‘ABOUT (xyz) WITHIN abc’.

ABOUT Query with CATSEARCH

Enter ABOUT queries with CATSEARCH using the query template method with grammar set to CONTEXT as follows:

select pk||' ==> '||text from test
where catsearch(text,
'<query>
  <textquery grammar="context">
     about(California)
  </textquery>
  <score datatype="integer"/>
</query>','')>0
order by pk;