relational language
Relational languages specify output in terms of
some property and some arguments. For example, if Tom has two
brothers, Dick and Harry, a relational language will respond
to the query "Who is Tom's brother?" with either Dick or
Harry. Notice that unlike {functional language}s, relational
languages do not require a unique output for each
{predicate}/argument pair. {Prolog} is the best known
relational language.
(1995-03-31)