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SEM: Light review of semantics document

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Wed, 06 Nov 2002 18:07:13 -0500
Message-ID: <3DC9A0A1.E6319D4@cse.lehigh.edu>
To: WebOnt <www-webont-wg@w3.org>

Here's some initial comments on the Semantics document dated Nov. 3:

1) Sect. 2.2. The syntax needs the ability to represent documents that
consist soley of facts (that is, something other than ontologies).
Perhaps a top-level <content> or <data> production could be added. The
most import reason for this is that content documents (which are not
ontologies), will also need to be represented. Assuming imports is not
postponed, such documents will also need to contain imports directives.

2) In the abstract syntax we have EquivalentClasses,
EquivalentProperties but SameIndividual. We should change them all to
the same basic form. Since sameXXXas is what is used in the exchange
syntax, I suggest: SameClass, SameProperty, and SameIndividual.

3) Section 3.4: The discussion of imports does not take into account
documents that are not ontologies. I had a proposal (that I thought you
agreed to), that fixed this and other problems. Is this an oversight, or
are you waiting for the group to resolve the issue before making a

4) Sect. 4.1: The conditino for n-triple form seem overly restrictive.
Is this just meant for OWL/DL?

5) Same section: The list of URI references that should not be mentioned
should include owl:imports (assuming it is not postponed)

6) Sect. 5.2: I'm hesitant about all of the iff definitions. For
example, isn't iff for TransitiveProperty putting an undue burden on
reasoners? I understand that you can only infer something is an
owl:TransitiveProperty if it is transitive in all models, but it seems
that you might be able uses cardinalities to restrict a property to a
certain number of tuples and then list all of these tuples. In such a
case, wouldn't complete reasoners always have to run through at the
tuples to determine if the property was transitive? Seems like an
expensive operation to me and I don't really see the utility of it.

Also, as I was reading the following thing occured to me, which is not
specific to the semantics document:

The notion of complementOf in an open-world like the Semantic Web
worries me. We can never compute the complement because we can never
know the entire set of resources. I guess this will be used in rules in
such a way that we never actually need to know the extension of the
complement of a class, but are we sure there are no problems lurking
here? Is this something that should be a new issue, or have people given
this enough thought and decided its okay?

Received on Wednesday, 6 November 2002 18:07:17 UTC

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