Re: Logical constraints in TM (Re: [topicmaps-comment] TAO vs. ERA)

[Murray Altheim <murray.altheim@sun.com>]

Bernard Vatant wrote:
> 
> Lars Marius, Tom
> 
> I think we drifted from the original thread to a wide new one, the question of logical
> constraints in TM.
[...]
> Those questions all boil down to the open question of how to express onto-logical
> constraints in topic maps. We have so far no way to check such inconsistencies as
> classification loops, no more indeed than to set and apply any other consistency or
> inference rule. That is the reason why AI people are so skeptical about topic maps,
> because they doubt that the underlying logical model can be clarified and extended to
> include needed consistency and inference rules. Setting rules for logical consistency of
> all associations in a topic map, not to speak about infering new associations from the
> existing ones, seems way more complex than doing the same for binary hierarchical
> relations of ontologies like class/instance and class/subclass.
> 
> Either we tackle that challenging issue as a whole, and IMO it's a task compared to which
> setting XTM syntax will appear as a walkover, either we let implementors develop
> proprietary and opportunist various solutions to implement rules for particular
> associations, corresponding to whatever they consider relevant : check (or not) for loops
> in classifications, allow (or not) multiple inheritance but declare inconsistency of
> certain types, constrain (or not) type of topics playing a given role, e.g. (rolespec, X,
> employee) => (topictype, X, people), set and check cardinality of members ... whatever ...
> and so much for interoperability.

The AI (and more generally, KR) community over the years has produced
many manifestations of ontological systems, syntaxes, etc. As you know,
I've spent some time looking into the Cyc ontology as well as others in
trying to figure out how to "re-represent" those existing semantics in 
XTM syntax, ie., not to reinvent the wheel but to take advantage of 
existing work. I believe it's possible to represent Conceptual Graphs
using XTM, and I've been lately investigating GXL as an XML graph syntax
that might actually work better. I know that it's possible to represent
XTM in GXL as I've done it (though only as an experiment). Having an
XTM document representing the basic CG core would enable inferencing
engines to operate upon XTM documents, just as they now do with CGIF.

Suffice it to say, XTM can be used as a foundation upon which existing 
KR systems can be built. The big difference between most KR systems and
topic maps are the mapping functions, but within a topic map system I
don't see any barriers to representing ontological relations, in fact
my Ph.D. proposal is based upon that. As to whether these need to be
standardized, and as to whether the PubSubj TC needs deal with any of
this, I don't feel strongly but rather doubt it.

Murray

...........................................................................
Murray Altheim, Staff Engineer          <mailto:murray.altheim&#64;sun.com>
Java and XML Software
Sun Microsystems, 1601 Willow Rd., MS UMPK17-102, Menlo Park, CA 94025

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