Predicate Queries

Another type of query is a predicate query. Predicate queries are used in those cases where exact matching is required, for instance when testing against a small fixed set of code values (for example, gender, race, and marital status) or when integers or floating point numbers must be matched as numeric values. A predicate query is just a predicate expression that returns a floating point value in the range 0.0 - 1.0 or a value that can be converted to a floating point value in the range 0.0 - 1.0 such as a Boolean value.

You can use variable attributes in predicate queries. A rich language is provided for creating predicate expressions, see Predicates for a complete description of predicate expressions and more details on their use as predicate queries. It can be combined with other types of queries into more complex query structures.

Predicate queries might encounter records with empty or invalid values. As with other queries, the match score in these cases is the empty score or invalid score respectively. Their behavior is the same as with other queries, they default to 0.0 and can be set to any preferred value.