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Re: proposal: Structured Datatypes

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 06 Nov 2002 14:52:28 -0500 (EST)
Message-Id: <20021106.145228.127869113.pfps@research.bell-labs.com>
To: connolly@w3.org
Cc: jonathan@openhealth.org, www-webont-wg@w3.org

I've made some changes to Johathan's message to try to make sense of it.


> On Tue, 2002-11-05 at 21:29, Jonathan Borden wrote:

[...]

> For the interim I propose when rdfs:range restrictions on
> owl:DatatypeProperty classes are URIs that identify XML datatypes [...]
> that the [values of this property] be elements of rdf:XMLLiteral and that
> are valid with respect to the particular XML datatype (e.g. XML Schema
> particle)
> 
> For example suppose the XML Schema particle
> 
> < xsd:complexType name =" xType " id="xType">
>  < xsd:sequence >
>    < xsd:element name ="a" type =" xsd:int " minOccurs =" 0 " />
>    < xsd:element name ="b" type =" xsd:string " minOccurs =" 0 " />
>  </ xsd:sequence >
> </ xsd:complexType >
> 
> then (modulo base URIs) the following is valid OWL
>
> <owl:DatatypeProperty rdf:ID="xDTprop">
>     <rdfs:range rdf:resource="#xType"/>
> </owl:DatatypeProperty>
> 
[...]
>
> <rdf:Description rdf:ID="foo">
>     <ex:xDTprop rdf:parseType="Literal">
>             <a>123</a>
>             <b>asdaasd</b>
>      </ex:xDTprop>
> </rdf:Description>
> 
> By this mechanism fragments of XML such as "<a>1234</a><b>asdasd</b>" which
> are valid w.r.t the type "#xType" and are considered individuals/members of
> the class "#xDTprop"
> 
> Jonathan

Unfortunately, there are several problems with this approach, aside from
the problem that Dan has identified.

First, the RDF, and thus the OWL, meaning for XML Schema built-in types is
incompatible with this meaning.  Second, XML literals in RDF are just
literals, not anything else, so there is very limited utility in the
scheme.  For example, if the element "a" had type int, <a>010</a> and
<a>0010</a> would be different.  Third, this approach would preclude any
attempt to do something better, like having the value above be a piece of
semi-structured data, containing an int and a string.

peter
Received on Wednesday, 6 November 2002 14:52:49 GMT

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