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Review of XML Schema Datatypes in RDF and OWL

From: Ashok Malhotra <ashok.malhotra@oracle.com>
Date: Mon, 11 Apr 2005 16:31:23 -0700
To: Ashok Malhotra <ashok.malhotra@oracle.com>, public-swbp-wg@w3.org
CC: w3c-xsl-query@w3.org
Message-ID: <20050411163123784.00000002636@amalhotr-pc>

Resending with subject line and improved formatting.

All the best, Ashok

> -----Original Message-----
> From: w3c-xsl-query-request@w3.org 
> [mailto:w3c-xsl-query-request@w3.org] On Behalf Of Ashok Malhotra
> Sent: Monday, April 11, 2005 4:12 PM
> To: public-swbp-wg@w3.org
> Cc: w3c-xsl-query@w3.org
> Subject: [w3c-xsl-query] <none>
> The W3C XQuery and XSLT WGs asked me to review the document 
> entitled XML Schema Datatypes in RDF and OWL.  The review 
> attached below has been approved by the WGs.  
> All the best, Ashok

> Review of XML Schema Datatypes in RDF and OWL (Editors' Draft 
> 2005/01/27)
> The RDF and OWL Recommendations use the simple types from XML 
> Schema and some of the operators from the F&O document. The 
> document we reviewed discusses three questions related to this usage: 
> - What URIref should be used to refer to a user defined datatype? 
> - Which values of which XML Schema simple types are the same? 
> - How to use the problematic xsd:duration in RDF and OWL?
> The document does not attempt to answer these questions in a 
> definitive manner but, rather, discusses the pros and cons of 
> different approaches.  
> Section 1.3
> This section refers to "derivation by list" and "derivation 
> by union".  This is, indeed, the XML Schema 1.0 usage but it 
> has caused widespread misunderstanding as the derived types 
> are not subtypes of the types they were derived from.  This 
> usage is being changed in XML Schema 1.1 to "constructed by 
> list" and "constructed by union".
> How to Refer to User-defined Datatypes
> Two approaches are discussed:  use the name of the derived 
> typed as a fragment identifier with the Schema target 
> namespace and the SCD approach recommended by XML Schema.
> Although it is not our place to make a recommendation here, a 
> couple of points need to be made.  The first approach speaks 
> about the using the URI "of the document".  This usage will 
> cause some members of the Schema WG extreme distress as they 
> take the position that Schemas are not isomorphic to 
> documents.  Thus, "schema target namespace" is recommended.
> The use of fragment identifiers is non-standard.  Although 
> others use fragment identifiers in non-standard ways the use 
> needs to be clearly delineated.
> The SCDs approach is the approach favored by the XML Schema 
> WG and, although the fragment identifier approach is simpler, 
> please look at the latest SCD draft from XML Schema.  It is 
> possible that they may be willing to enter into a dialog and 
> make changes to the SCD draft to accommodate your needs better. 
> 3 Comparison of Values
> There is an extended disquisition on equivalence of values.  
> Not much new here.  But please look at the newly introduced 
> promotion scheme from xs:anyURI to xs:string.  Please also 
> note that xs:hexBinary can be cast to xs:base64Binary and 
> that comparisons on values of these two types can be made 
> after casting. 
> 3.5 eq
> The document says that 'eq' returns 'true' or 'false' or that 
> the values are not comparable.  This is not the case.  The 
> 'eq' operator returns a type error if the values are 
> incomparable and returns the empty sequence if one or both 
> operands is the empty sequence.
> The final example is incorrect "INF"^^xsd:float eq 
> "INF"^^xsd:float does return 'true'.
> Please use the F&O functions to test for equality.
> 4. Duration
> The document discourages the use of xs:duration and instead 
> recommends the use of xdt:dayTimeDuration and 
> xdt:yearMonthDuration.  We agree.
> .
Received on Monday, 11 April 2005 23:31:39 UTC

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