language(smalltalk).
language(lisp).
language(prolog).

essence(smalltalk,objects,'message passing').
essence(lisp,lists,'recursive functions').
essence(prolog,relations,'logical inferencing').

history(smalltalk,inventor('Alan Kay'),date(1980)).
history(lisp,inventor('John McCarthy'),date(1959)).
history(prolog,inventor('Alan Colmeraur'),date(1971)).