- From: Benjamin Nguyen <Benjamin.Nguyen@inria.fr>
- Date: Mon, 28 Nov 2005 18:00:51 +0100 (CET)
- To: "Jeff Z. Pan" <jpan@csd.abdn.ac.uk>
- cc: SWBPD <public-swbp-wg@w3.org>
On Mon, 28 Nov 2005, Jeff Z. Pan wrote: > > > Let me clarify the two proposals. > > 1) Primitive equallity: all XML Schema datatypes have disjoint value spaces. > > 2) Primitive equality extended with approximate mappings (easlier known as "leave it to the application"): it is more general than 1). Now all XML Schema datatypes have disjoint value spaces, plus applications can specify some approximate mappings, such as mapping "1.3"^^xsd:float to "1.3"^^xsd:double. Surely a best practice would be to ask applications **not** to map xsd:float to xsd:double, but allow xsd:double to xsd:float, or any type promotion legal wrt XPath, or at least suggest something, such as returning the fact the result was calculated using an approximate mapping. > > Note that in this case, the values of "1.3"^^xsd:float and "1.3"^^xsd:double are different, but the approximate mapping **enables** the use of the XPATH eq operator, such as in the following SPARQL query: > > > SELECT ?size > > WHERE { eg:car eg:engineSizeInLitres ?size . > > FILTER (?size = xsd:decimal("1.3") ) . } > > Using 2), "1.3"^^xsd:float and "1.3"^^xsd:double could be results of the above query with the help of approximate mappings. > > Another benefit of 2) is interoperability. Consider the scenario where one map ontology use xsd:float as the range of milage while the other use xsd:double. Using 1), milages in all different. While using 2), approximate mappings allows applications to do some useful things. Fully agree with benefits. > > We have briefly addressed how to formalise the approximate mappings in our draft, see: > > http://www.w3.org/TR/swbp-xsch-datatypes/#sec-values-eq See my previous comments (and Jeremy's comments ) at : http://lists.w3.org/Archives/Public/public-swbp-wg/2005Nov/0055.html > > Finally, the 2) approach is not non-monotonic. Even if we map"1.3"^^xsd:float to "1.3"^^xsd:double, their interpretations are still different. It would be non-monotonic if their interpretations became equal to each other after the mapping. Unsure here, will detail later. > > Jeff > > -- > Dr. Jeff Z. Pan (http://www.csd.abdn.ac.uk/~jpan/) > Department of Computing Science, The University of Aberdeen > ------------------------------------ | Dr. BENJAMIN NGUYEN | | Université de Versailles | | et St-Quentin-en-Yvelines | | Eq. Systèmes de Bases de Données | | 45, av des Etats-Unis | | 78035 Versailles CEDEX | |----------------------------------| | INRIA-Futurs | | Projet Gemo | | 4, rue Jacques Monod | | ZAC des Vignes | | 91893 Orsay CEDEX | | FRANCE | ------------------------------------ Tel. INRIA : (33) (0) 1 72 92 59 31 Tel. UVSQ : (33) (0) 1 39 25 40 49
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