Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!mcvax!philmds!philtis!debruyn From: debruyn@philtis.UUCP (F.W.G.M. de Bruyn @ Philips CAD Centr) Newsgroups: comp.lang.prolog Subject: Re: Behavior of assert and retract Message-ID: <237@philtis.UUCP> Date: Thu, 16-Jul-87 07:29:49 EDT Article-I.D.: philtis.237 Posted: Thu Jul 16 07:29:49 1987 Date-Received: Sat, 18-Jul-87 05:58:42 EDT References: <3287@bigburd.PRC.Unisys.COM> <19702@ucbvax.BERKELEY.EDU> Reply-To: debruyn@philtis.UUCP Organization: Philips - CAD Centre, Eindhoven, The Netherlands Lines: 25 Keywords: backtracking to retract In article <19702@ucbvax.BERKELEY.EDU> citrin@ji.Berkeley.EDU.UUCP (Wayne Citrin) writes: >clauses of needs_visiting/1 than when it can. I favor fixing the visible >clauses at the time that the choice point is created since this seems to make >it easier to make informal 'assertions' about the behavior of the code >(in other words, to understand what's going on). I don't think this should be used as an argument in favour of fixing the set of branch destinations in a choice point at the moment of calling. Facilities for hypothetical reasoning (that's what's being asked for) should be implemented through a partitioned clause-base (in other words: modularity). It would be interesting to learn from Fernando Perreira (C-prolog) and Richard o'Keefe (ok@quintus.uucp) what arguments pro and con they weighed when opting for this route. -- +---------------------------------------------------------------------------+ | Frank W.G.M. de Bruyn, Philips Advanced Developments/ Applied AI | | PO. box 218, Rm. HKJ P830, NL-5600 MD Eindhoven, THE NETHERLANDS | | ARPA/CSNET: mcvax!philtis!debruyn@seismo.css.gov | | BITNET/EARN/EAN/JUNET: debruyn@philtis.uucp | | USENET/EUNET/ACSNET: {seismo, munnari}!debruyn@philtis.nl | | JANET: ukc!mcvax!philtis!debruyn | +---------------------------------------------------------------------------+