Path: utzoo!mnetor!uunet!mcvax!unido!tub!tmpmbx!netmbx!morus
From: morus@netmbx.UUCP (Thomas M.)
Newsgroups: comp.ai
Subject: Re: Student versions of OPS5
Message-ID: <1580@netmbx.UUCP>
Date: 25 Mar 88 18:05:25 GMT
References: <1110@pembina.UUCP> <1501@netmbx.UUCP> <27336@aero.ARPA>
Reply-To: morus@netmbx.UUCP (Thomas Muhr)
Organization: netmbx Public Access Unix, Berlin
Lines: 39
Keywords: OPS5, IBM PC/XT/AT

In article <27336@aero.ARPA> srt@aero.UUCP (Scott R. Turner) writes:
>In article <1501@netmbx.UUCP> muhrth@db0tui11.BITNET (Thomas Muhr) writes:
>>I have now available a few common-lisp
>>sources (each about 100KB big) which I will try to convert to a PC-runnable
>>version in the near future.
>
>It should be possible to write an OPS5-like language in a lot less than 
>100K.  The only difficult part of OPS5 to implement is the RETE algorithm.
>Throw that out, ignore some of the rules for determining which rule out 
>of all the applicable rules to use (*), and you should be able to implement
>OPS5 in a couple of days.  Of course, this version will be slow and GC 
>every few minutes or so, but those problems will be present to some extent
>in any version written in Lisp.

Right, but after all the proposed deletions this code would hardly cover 2
pages. Leaving Rete-match out is not just affecting run-time (the decrease
in performance is incredible!) - but it would eliminate all features which
make OPS5 an interesting language - mainly the heuristics for selecting
rule-instantiations intelligently. 
>
>(*) My experience is that most OPS5 programmers (not that there are many) 
                                Is this right ? ---^^^^^^^^^^^^^^^^^^^^^^
>ignore or actively counter the "pick the most specific/least recently used"
>rules anyway.
Well, it would be fine to have a little more influence on conflict-resolution
strategies - but the mentioned ones are very important: 
Default strategies via "specifity", controlling loops via "recency" are very
powerful features.
Ignoring these mechanisms means that they have chosen the wrong paradigm.

-------- Thomas Muhr

Knowledge Based Systems Group
Technical University of Berlin
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