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Re: Non-global Keys

From: Jim Hendler <hendler@cs.umd.edu>
Date: Tue, 15 Jul 2003 13:53:26 -0400
Message-Id: <p05200f52bb39efee309a@[]>
To: Bob MacGregor <macgregor@ISI.EDU>, public-webont-comments@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
>   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.
>RAISED BY: J. Hendler based on a Last Call comment raised by Bob 
>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 

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

[2] http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0085.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)
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Received on Tuesday, 15 July 2003 13:53:34 UTC

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