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 McCarth'), date(1959)).
history(prolog, inventor('Alan Colmeraur'), date(1971)).