DB2 Version 10.1 for Linux, UNIX, and Windows

Predefined thesaurus relations

The Net Search Extender contains predefined relations which include associative relations, synonym relations, and hierarchical relations.

Associative relations
An associative relation is a bidirectional relation between two terms that do not express the same concept but relate to each other.

Predefined associative relation: RELATED_TO
Examples:
```
tennis RELATED_TO racket
football RELATED_TO goal (sports)
```
Synonym relations
A synonym relation is a bidirectional relation between two terms that have the same or similar meaning and can be used as alternatives for each other. This relation can, for example, be used between a term and its abbreviation.

Predefined synonym relation: SYNONYM_OF
Examples:
```
spot SYNONYM_OF stain
US   SYNONYM_OF United States
```
The figure in Figure 1 shows two goal terms in the same thesaurus. One is specified with the comment (sports), the other with the comment (abstract). Even if terms have the same spelling, synonym relations can connect different word groups. You can model this by using different relations when defining the thesaurus.
Hierarchical relations
A hierarchical relation is a unidirectional relation between two terms, one of which has a broader (more global) meaning than the other. Depending on its direction, the relation can be used to look up either more specialized or more global terms.
Predefined hierarchical relations:
- LOWER_THAN to model narrowing relations
  LOWER_THAN relations are for modelling a sequence of more specialized terms. The deeper you follow a narrowing relation, the more specific the terms become. For example, if you look up the term ball game along a LOWER_THAN relation, the result could be squash tennis and so on, in a list of increasingly specialized terms.
- HIGHER_THAN to model broadening relations
  HIGHER_THAN relations are for modelling a sequence of more and more global terms. The deeper you follow such a relation, the less specific the terms become. For example, if you look up the term ball game along a HIGHER_THAN relation, the result could be game and so on, in a list of increasingly global terms.