From: Jeremy Carroll <jjc@hpl.hp.com>

Date: Mon, 12 Nov 2007 20:24:41 +0000

Message-ID: <4738B689.6040305@hpl.hp.com>

To: public-owl-wg@w3.org

Date: Mon, 12 Nov 2007 20:24:41 +0000

Message-ID: <4738B689.6040305@hpl.hp.com>

To: public-owl-wg@w3.org

6) Various decidable subsets are possible, but no basis for making choices Assuming the design is fixed to permit referring to some n-ary datatypes, then there are many different choices for n-ary datatypes over which it is in principle possible to reason. Carsten points out: [[ 1. the integers with addition, equality, and equality to constants 2. the integers with multiplication, equality, and equality to constants Both of them are useful and decidable (1. can be reduced to integer programming or Presburger arithmetic, and 2. to Skolem arithmetic) but together they are not because of Hilbert 10. ]] further possibilities are to restrict oneself to only finite datatypes, such as float, int, ... which being finite are necessarily decidable (although practical optimization may be challenging). Carsten suggests: [[ Would it be a solution to give a couple of (alternative) datatypes that OWL1.1 could support, and also to point out the combinations that cause troubles? I feel that being liberal here is fine, because in the end it boild down to what you reasoner supports anyway. ]] This seems to me to miss the point: - a W3C specification is provided to provide interopertation between reasoners - a W3C specification is provided to allow interoperation between data from different sources - without guidance from a specification, the reasoner vendors have all decided to implement the same datatype group, the one that contains no datatypes: this is the one that is ready for standardization. I feel that the analysis provided by Turner and Carroll demonstrates conclusively that we do not know how to provide such interoperation, and hence the area of n-ary datatypes is either unsuited to standardization or is being put forward for standardization prematurely. In either case the solution for this WG is to support only 1-ary datatypes, and to postpone the issue awaiting further research.Received on Monday, 12 November 2007 20:25:12 GMT

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