- From: Dave Reynolds <der@hplb.hpl.hp.com>
- Date: Wed, 25 Mar 2009 22:16:45 +0000
- To: Sandro Hawke <sandro@w3.org>
- CC: RIF WG <public-rif-wg@w3.org>
Sandro Hawke wrote: >> For OWL then they define xsd:dateTimeStamp to have a value space >> corresponding to a timeline instead of following the XML Schema 1.1 >> structural model and so for OWL's definition identity and equality >> coincide again. > > Actually, XSD put the timezone into the value space, and today OWL > agreed to go along with that. Ugh. [I was going by the OWL wiki.] > I don't like the outcome -- if a meeting > ontology says a meeting can have one start time, and the same time is > expressed twice, with different time zones, the ontology is inconsistant Quite. > -- but I don't see a way to fix it given how XSD and OWL each see the > world, so I supported the decision. > > My hope is that RIF is allowed more flexibility, and we can have > identity, equality, and equivalence. Or maybe we can settle on two of > the three, but I'm pretty sure users need (and existing rule systems > provide) Identity and Equivalence. The existing XPath operators already in DTB give us equivalence for the the types that are of interest. RIF "=" and the pred:literal-not-equal (as already defined in DTB) give us the identity and converse. I think that's enough. Dave > - s > >> So my contention is that the way literal-not-equal is defined in DTB at >> present (non-identity) corresponds to the equality notion in OWL for all >> the relevant datatypes and I keep my preference for options 2 or 1 [4]. >> >> This contention is trivially true if we stick to XML Schema 1.0 because >> there is no distinction between equality and identity there. If we move >> to XML Schema 1.1 (is there a proposal to do this? I assume so) there >> are differences but the main problematic datatype is not included in OWL[5]. >> >> Dave >> >> [1] http://www.w3.org/TR/xmlschema11-2/#value-space >> "For purposes of this specification, the value spaces of primitive >> datatypes are disjoint, even in cases where the abstractions they >> represent might be thought of as having values in common." >> >> [2] http://www.w3.org/TR/xmlschema11-2/#value-space >> "Note: In the prior version of this specification (1.0), equality was >> always identity. This has been changed to permit the datatypes defined >> herein to more closely match the "real world" datatypes for which they >> are intended to be used as transmission formats." >> >> [3] I don't know what a good name for this is so I'm using "equivalence" >> for now. You could call it "programmatic equality" or "pragmatic >> equality" or something. >> >> [4] http://lists.w3.org/Archives/Public/public-rif-wg/2009Mar/0076.html >> >> [5] OK, that does leave the corner cases of float/double (-0 = +0, Nan >> != NaN) I haven't checked how OWL handle these. If those are the only >> differences then I personally don't care either way. >> -- >> Hewlett-Packard Limited >> Registered Office: Cain Road, Bracknell, Berks RG12 1HN >> Registered No: 690597 England >>
Received on Wednesday, 25 March 2009 22:17:30 UTC