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Re: Case for Reinstatement of Qualified Cardinality Restrictions

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 23 Apr 2003 14:59:38 -0400 (EDT)
Message-Id: <20030423.145938.14935386.pfps@research.bell-labs.com>
To: heflin@cse.lehigh.edu
Cc: www-webont-wg@w3.org

From: Jeff Heflin <heflin@cse.lehigh.edu>
Subject: Re: Case for Reinstatement of Qualified Cardinality Restrictions
Date: Wed, 23 Apr 2003 14:29:15 -0400

> Peter,
> 
> Guus's comment got me thinking. My original message was based on what
> was true for DAML+OIL, and I just assumed it wasn't changed in OWL
> because I didn't remember it coming up as an issue. However, I started
> poking around in the AS&S section 4, and don't see a transformation from
> the abstract syntax that would produce a piece of RDF syntax in which an
> owl:Restriction had a combination of owl:cardinality, owl:allValuesFrom,
> owl:someValuesFrom, etc. The only way this could happen is if different
> restrictions could have the same main node, but I'm assuming that the 
> "_:x" notation means a blank node, which you say must be local to each
> transformation. If the RDF syntax of OWL is only those RDF graphs that
> can be produced from abtract OWL ontologies by applying the
> transformation rules, then it seems that Guus is right (if I'm wrong
> please point out how the transformation can be performed or where my
> assumptions went astray).

I don't see such a transformation.  There is abstract syntax of the form
	restriction(foo cardinality(5) allValuesFrom(bar))
but this translates into an intersection.

> In any case, this exercise has led me to believe we need to do two
> things with the OWL specs. First, I think the reference needs to discuss
> what is the preferred way for writing multiple restrictions on a single
> property (I assume this is as an intersectionOf Restrictions, although
> this is very ugly, and I much prefer the syntax used in my previous
> message, if it's legal and correct OWL).

The only reasonable way to write multiple restrictions on a single property
in the RDF encoding is with an intersection.  It would have been nice to
not have to do this, but our hands were tied.

> Second, although the AS&S makes it easy to transform from the abstract
> syntax to RDF, I think it is much harder to do the reverse
> transformation (which actually seems like a more common one). I think it
> would be nice to have a table that presents this transformation. This
> may also be useful in placating people who ask "where's the official
> syntax?"

There is a proposal for such a reverse translation from Jeremy.

> Jeff
Received on Wednesday, 23 April 2003 14:59:51 GMT

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