A Constraint-Based Language for Querying Taxonomic Systems
Oct 1991
This paper presents a language for querying taxonomic systems which is essentially a variant of first-order logic with terms denoting types instead of individuals. A query expressed in the language is either a declarative or an interrogative sentence. Declarative sentences correspond to the usual first-order formulae and require a “yes” or “no” answer. Interrogative sentences are basically declarative sentences with some variables stipulated as “query” variables, for which the required answers are type assignments to the query variables making the sentences true. From the semantic point of view, queries will be interpreted as type constraints on the query variables, and answers as constraints in a specified normal form called “solved” form. To that effect, the paper proposes a general scheme for constraint programming based on the notions of constraint satisfaction and constraint reduction, and shows how the query language can be viewed as an instance of the scheme. This constraint system is the basis of a constraint logic programming system dealing with type information as described by taxonomies.
