occurs check in prolog

From: feffo (st10674_at_student.uib.no)
Date: 01/15/04 

Date: 15 Jan 2004 14:41:20 -0800

hi,
i would like to know, since i haven't been able to find enough
information around, if there exist a version of prolog(or another
logic language) that implements the occurs check for the unification
(excluding the function: unify_with_occur_check()) with a certain
efficency, or at least if there are comparative studies on the
subject, to check if it's actually so bad to use this test instead of
other tricks, and make prolog sound.
I've been asked to do a study on the problem, check the efficency of
prolog with different occurs check algorithms, and find out if the
efficency goes down really so much, or it's possible to find an
acceptable solution.
So i wondered, is it possible that noone ever thought to carry on such
a research or at least made an attempt?!how did they decided then, not
to use this test at all and leave prolog unsound?
I would really appreciate a help.

Thanks to all the ones who will answer.