- From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
- Date: Mon, 06 Jan 2003 19:49:54 +0000
- 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 UTC