Graphic/Representation Artifacts

fritz@rodin.wustl.edu (Fritz Lehmann)

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Date: Tue, 17 May 94 07:22:32 CDT
From: fritz@rodin.wustl.edu (Fritz Lehmann)
Message-id: <9405171222.AA04134@rodin.wustl.edu>
To: cg@cs.umn.edu, interlingua@ISI.EDU, srkb@ISI.EDU
Subject: Graphic/Representation Artifacts
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     Sarris, and Sowa (I think), have been right about separating
different levels of representation.  It is important to be clear
about what is central to semantic meaning versus the artifacts
of various representations.  In the database field there is a
growing consensus in favor of the "three-schema model". Schema
1 is the "conceptual schema" which is the central abstract
semantic structure and ontology (which really floats in a Platonic
space*); schema 2 is the presentation schema, which concerns all
external interactions with the system and symbolic or graphic
representations, and "user views"; schema 3 is the implementation
level which deals with how the system is actually embodied in
a real machine or network of machines.  Although all three are
related and must affect one another, they are specified
separately, and the specification of any one should not be
encrusted with artifacts from the others.

     This is a valuable model to keep in mind in discussions
of conceptual graphs and "PEIRCE", and of the Knowledge Sharing
Effort.  I think the recent CG discussion highlights this fact.
We shouldn't confuse the three schemas.


                          Yours truly,   Fritz Lehmann

(*Note to Len Schubert: hence there are no arbitrary orderings
on essentially unordered things -- symmetries are preserved.)

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