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Re: LANG: Defn of DL in Mappings

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Mon, 06 Jan 2003 19:49:54 +0000
Message-ID: <3E19DDE2.6030805@hpl.hp.com>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
CC: hendler@cs.umd.edu, www-webont-wg@w3.org

Jeremy:

>>>> I think the abstarct syntax could benefit
>>>> from the following change:
>>>>
>>>> In many places (to be defined precisely which)
>>>> replace
>>>>   <URI reference>
>>>> with
>>>>   <OWL Name>
>>>>
>>>> and add a rule
>>>>
>>>> <OWL Name> ::= <URI Reference>
>>>> <OWL Name> ::= <local identifier>
>>>>
>>>> The latter play the same role in the abstract syntax as Blank node
>>>> identifiers play in N-triples and RDF/XML. (Note there are no blank node
>>>> identifiers in the RDF graph).
>>>>
>>>
>>>> This when combined with 2(b) allows near-arbitrary use of blank nodes while
>>>> clearly remaining within the constraints of the abstract syntax.
>>>>


Peter:

> 
> Because loops in descriptions can easily break OWL/DL.  Determining the
> constraints under which this will happen is, in my expert opinion, a
> difficult task that will, even if done correctly, produce no benefits.
> 


This proposal does not introduce any new loops into the abstract syntax.

Given an OWL abstract syntax document in which _:alphanumericstring is used 
as a local identifier as above (noting that this is not a valid URI 
reference), and supposing w.l.o.g. that no URI with the prefix 
"http://arbitrary/foo#" occurs in the abstract syntax, we can replace every 
occurrence of _:alpha with http://arbitrary/foo#alpha.
Under my proposal the document before such replacement has loops if and 
only if the document after replacement has loops.

Hence a discussion about loops in descriptions is specious.

There is a change in the semantics of the document in that one cannot 
rename URIs and have the same meaning; under the OWL Full semantics there 
are no bnode labels and so you can change these labels. So to continue to 
support the semantic layering resolution we may need to use a technique 
like Pat uses in the RDF model theory to treat the bnode as an existential 
qualification. This would happen in the semantics of the abstract syntax 
section.

Jeremy
Received on Monday, 6 January 2003 14:50:22 GMT

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