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Proposed simplification of datatype expressions

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Thu, 13 Mar 2003 16:47:26 +0000
Message-ID: <15984.46622.39548.462734@merlin.horrocks.net>
To: www-webont-wg@w3.org

I know this is rather last-minute, but I would like to propose a
couple of small simplifications to the language that would
significantly improve ease of implementation of datatype reasoning in
both DL and Lite.

1. Change the specification of cardinality constraints so that they
can only be applied to individual valued properties and not to data
valued properties. This seems to be a relatively small loss as most
data valued properties turn out to be functional, and it is hard to
think of realistic examples where local/arbitrary-valued cardinality
constraints are required.

2. Eliminate the dataRange construction from OWL DL, i.e., do not
support oneOf(5 10 15 20). If used in someValuesFrom restrictions,
this construction doesn't add any expressive power as it is equivalent
to a disjunction of value restrictions, but if used in allValuesFrom
restrictions it acts like a datatype definition outside XMLS.


These changes would significantly simplify the task of implementing
datatype reasoners:

- There would no longer be any need to worry about interactions between
  cardinality constraints and the cardinality of a datatype, and a
  datatype reasoner would not have to consider multiple sets of
  constraints, each of which must have a different solution;

- A datatype reasoner would only need to consider the satisfiability
  of a finite conjunction of (possibly negated) type specifications
  and values, and would not need to deal with disjunctions of such
  conjunctions.

- It would be much easier to extend the language to deal with nary
  datatypes, e.g., to compare the values of multiple properties -
  combining these with cardinality constraints gets quite hairy
  because it is necessary to count all possible tuples that can be
  formed from the relevant properties.


Regards, Ian
Received on Thursday, 13 March 2003 10:46:41 GMT

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