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Re: Issue 80: terminology

From: Sandro Hawke <sandro@w3.org>
Date: Wed, 25 Mar 2009 14:55:57 -0400
To: Dave Reynolds <der@hplb.hpl.hp.com>
cc: RIF WG <public-rif-wg@w3.org>
Message-ID: <19761.1238007357@ubehebe>

> 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.  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
-- 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.

     -  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.
> -- 
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Received on Wednesday, 25 March 2009 18:56:05 GMT

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