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)).