relational language
<language> Any kind of {programming language} that specifies
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
languages}, relational languages do not require a unique
output for each {predicate}/argument pair. {Prolog} is the
best known relational language.
(2004-05-17)