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From: finin@prc.unisys.com (Tim Finin)
Newsgroups: comp.lang.prolog
Subject: Re: hierarchy among modules in prolog
Keywords: modules, hierarchy, inheritance
Message-ID: <11672@burdvax.PRC.Unisys.COM>
Date: 9 Oct 89 15:10:03 GMT
References: <5641@portia.Stanford.EDU>
Sender: news@PRC.Unisys.COM
Reply-To: finin@prc.unisys.com (Tim Finin)
Organization: Unisys Paoli Research Center, PO Box 517, Paoli PA 19301
Lines: 38
In-reply-to: sreerang@portia.Stanford.EDU (Sreeranga Rajan)

In article <5641@portia.Stanford.EDU>,sreerang@portia(Sreeranga Rajan) writes:
>I would like to know if it is possible to make the visibility of
>assertions in modules hierarchical in prolog. The prolog I am using
>being Quintus prolog running on Sun-unix, seems to have a flat
>module system. Would there be any other prolog where its possible to
>have a hierarchical module system? Any input on this is greatly appreciated.

As Richard pointed out, there are many possible notions of a
"hierarchical module system".  We've explored one possibility that is
motivated more from a AI knowledge representation and reasoning
perspective than from a programming language one.  We have a
forthcoming paper on this:

  Finin, Tim and James McGuire, ``Inheritance Hierarchies in Logic
  Programming Languages'', in Inheritance Hierarchies in Knowledge
  Representation, M.  Lenzerini, D. Nardi and M. Simi (eds.), Wiley, 1990.

Which is available in draft form as Technical report PRC-LBS-8812
which can be obtained by contacting Judy Norton, Unisys Paoli Research
Center, Box 517, Paoli PA 19301.  Here is the paper's abstract:

  This paper presents an extended model for a logic programming
  language's knowledge base.  Instead of being restricted to one global
  knowledge base, as is the case with Prolog, we allow segmentation into
  units which are linked together into a lattice.  Each unit defines a
  view on the knowledge base which includes those clauses which have
  been asserted into that unit as well as clauses inherited from its
  ancestors higher in the lattice structure.  This model supports
  arbitrary retraction.  Retracting a clause in a knowledge base unit
  effectively blocks its inheritance for that unit and all of its
  descendants. Motivations for using this model are given.  We also
  discuss the design-iterations of a Prolog-based implementation (Phd)
  of this model.
-- 
______________________________________________________________________________
Tim Finin                     finin@prc.unisys.com (internet)
Unisys Paoli Research Center  ..!{psuvax1,sdcrdcf,cbmvax}!burdvax!finin (uucp)
PO Box 517                    215-648-7446 (office), 215-386-1749 (home),