- From: Jim Hendler <hendler@cs.umd.edu>
- Date: Thu, 3 Jul 2003 16:15:26 -0400
- To: Dan Connolly <connolly@w3.org>, Guus Schreiber <schreiber@cs.vu.nl>
- Cc: webont <www-webont-wg@w3.org>
Dear Bob- Thank you for your comment, the working group has considered it carefully. With respect to qualified keys, we considered how this could be added to OWL - see the discussion thread starting at [1] and particularly [2]. The group considered the addition of Qualified Cardinality Restrictions, which we believe are needed to implement the sort of global keys you need. However, the WG decided to postpone the issue of QCRs as discussed in my response to Alan Rector at [3]. We also considered the issue of Compound Keys. We decided this was an important enough area to open an issue on our issues list explicitly. We did not, however, come up with a solution as to how to address these. Instead we also decided to postpone this issue. The issue text is: >TITLE: Compound Keys >DESCRIPTION: > Relational Databases often use keys that are composed of multiple >fields. OWL allows keys using owl:InverseFunctionalProperty for a >single field (property). It would be desirable for OWL to provide >the compound keys capability as well. >STATUS: POSTPONED >RAISED BY: J. Hendler based on a Last Call comment raised by Bob >MacGregor: >http://lists.w3.org/Archives/Public/public-webont-comments/2003May/0019.html > >Closing Comments: > >While compounds keys would be desirable to add, there is some >difficulty in adding them in the current OWL syntax, similar to the >problem arising for "qualified" properties (see discussion under >issue 3.2). In addition, for the OWL DL profile, it is still >something of a research issue (c.f. >http://www.dis.uniroma1.it/~calvanes/papers-html/DL-2000.html) as to >how these are best realized by DL reasoners. There is also a >question as to whether mixing datatype and object type in a compound >key would be allowed, and whether it would cause difficulties to >reasoners. > Please let us know if this decision to (a) acknowledge that our design is lacking, but (b) postpone further design work to a future version is acceptable. -Jim Hendler [1] http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0064.html [2] http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0085.html [3] http://lists.w3.org/Archives/Public/public-webont-comments/2003Jun/0024.html -- Professor James Hendler hendler@cs.umd.edu Director, Semantic Web and Agent Technologies 301-405-2696 Maryland Information and Network Dynamics Lab. 301-405-6707 (Fax) Univ of Maryland, College Park, MD 20742 *** 240-277-3388 (Cell) http://www.cs.umd.edu/users/hendler *** NOTE CHANGED CELL NUMBER ***
Received on Thursday, 3 July 2003 16:15:42 UTC