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Re: Smart Literal proposal

From: Graham Klyne <gk@ninebynine.org>
Date: Sun, 24 Oct 2004 18:17:46 +0100
Message-Id: <5.1.0.14.2.20041024181356.030ba338@127.0.0.1>
To: charles@w3.org
Cc: "Stephane Fellah" <fellah@pcigeomatics.com>, www-rdf-interest@w3.org

Chaals,

Yes, I agree that's another approach.  See also [1], which has some 
examples of something like this.  I don't yet have a clear idea about 
whether I prefer this to interpretation properties for capturing things 
like units of measure.

#g
--

[1]  Horrocks, I. and J. Pan, "Web Ontology Reasoning with Datatype 
Groups", 
2003.  http://www.cs.man.ac.uk/~horrocks/Publications/download/2003/PaHo03a.pdf


At 06:21 24/10/04 -0400, charles@w3.org wrote:
>You could just use rdf:datatypes which are defined as being a length in
>metres expressed as a "float". See
>http://www.w3.org/2001/sw/Europe/200409/geox for some examples of how I
>set about doing this.
>
>I asked DanC why he did InterpretationProperties instead and he said it
>was because cwm had a bug in handling datatypes. I believe Jena, for
>example, has no such problem. I also think they are useful things...
>
>cheers
>
>chaals
>
> >
> > Stephane,
> >
> > (I'm responding to just the first few lines of your message.  I haven't
> > studied your example.  Please ignore if not helpful.  Also, trimmed reply
> > list.)
> >
> > See also, "interpretation properties":
> >    http://www.w3.org/DesignIssues/InterpretationProperties.html
> >
> > #g
> > --
> >
> > At 16:23 22/10/04 -0400, Stephane Fellah wrote:
> >
> >>Hi,
> >>
> >>
> >>
> >>I am trying currently to qualified literal with more attributes than
> >>xml:lang and rdf:datatype.
> >>
> >>
> >>
> >>In RDF, there are two three types of literal.
> >>
> >>
> >>
> >>* Plain Literal, which consists of a string with an optional attribute
> >>xml:lang
> >>
> >>* Typed Literal, which is a string with rdf:datatype attribute.
> >>
> >>* XML Literal, which is a literal representing an XML literal.
> >>
> >>
> >>
> >>Sometimes, it is necessary to qualified further a typed Literal without
> >>creating a resource. For example, a unit of measure or a codespace
> >>(taxonomy) in which the value belongs to (tree name taxonomy for
> >> example).
> >>The only way to describe these attributes in the current RDF
> >>specification, is to create an anonymous resource having these different
> >>properties. This makes the serialization of RDF in XML pretty lengthy and
> >>ugly to read by human.
> >>
> >>
> >>
> >>Here an example (in a sloppy syntax, I apologize)
> >>
> >>
> >>
> >><Road>
> >>
> >>    <length>
> >>
> >>         <value rdf:datatype="&xsd;float">10</value>
> >>
> >>         <gml:uom rdf:resource="urn:opengis:uom:meter">
> >>
> >>    <length>
> >>
> >>    <surfaceType>
> >>
> >><value>asphalt</value>
> >>
> >><gml:codespace rdf:resource= urn:ataxonomyofsurfacetype />
> >>
> >>    </surfaceType>
> >>
> >><Road>
> >>
> >>
> >>
> >>A more elegant way to serialize this would be:
> >>
> >>
> >>
> >><Road>
> >>
> >>       <length gml:uom="urn:opengis:uom:meter"
> >> rdf:datatype="&xsd;float">10</length >
> >>
> >>       <surfaceType  gml:codespace=
> >> urn:ataxonomyofsurfacetype >asphalt</surfaceType>
> >>
> >><Road>
> >>
> >>
> >>Please note that this syntax will bridge some gaps with current XML
> >>document syntax defined in XML schema.
> >>
> >>
> >>
> >>The problem with this syntax is that RDF parsers such as ARP or Jena,
> >>would return an error because no other property attribute can be used
> >> with
> >>rdf:datatype.
> >>
> >>
> >>
> >>In RDFS, a literal is a subclass of Resource, however most of RDF API
> >> does
> >>not use the same hierarchy. In Jena for example, Literal is subclass of
> >>RDFNode and not Resource. So it does not provide the ability to add
> >>additional properties to a literal. However, if we follow the ontology, I
> >>should be able to add either annotation property to Literal or subclass
> >>the class Literal with additional properties (probably would be in OWL
> >>Full in this case).
> >>
> >>
> >>
> >>If a Literal was a subclass of resource, the former RDF example could be
> >>represented in a canonical way:
> >>
> >>
> >>
> >><Road>
> >>
> >>    <length>
> >>
> >>         <Literal>
> >>
> >>            <rdf:datatype rdf:resource="&xsd;float"/> (this is an
> >> extension of rdf)
> >>
> >>            <rdf:lexicalform>10</rdf:lexicalform>  (this is an extension
> >> of rdf)
> >>
> >>            <gml:uom rdf:resource="urn:opengis:uom:meter"/>
> >>
> >>         <Literal>
> >>
> >>    <length>
> >>
> >><Road>
> >>
> >>
> >>
> >>Note that rdf:datatype and rdf:lexicalform does not seem to be defined in
> >>RDFS or RDF, but may be needed to support RDF API.
> >>
> >>
> >>
> >>This form would be equivalent to the previous compact example. The only
> >>constraint we would have to the literal interface is to have properties
> >>with resource URI or string values. May be they should be annotation
> >>properties. Technically, tuning existing a parser to support this
> >>extension would not be a big job. The question is whether this is valid
> >>with RDF semantics or not.
> >>
> >>Is there any reason why this could not be done ? Does my reasoning make
> >>sense ? Is the proposal acceptable to improve RDF specification? Does not
> >>anyone experiment such an approach ?
> >>
> >>
> >>
> >>Best regards
> >>
> >>
> >>
> >>Stephane Fellah
> >>
> >>Web Chief Architect
> >>
> >>PCI Geomatics, Hull, QC
> >>
> >>
> >>
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> >>
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> >
> > ------------
> > Graham Klyne
> > For email:
> > http://www.ninebynine.org/#Contact
> >
> >

------------
Graham Klyne
For email:
http://www.ninebynine.org/#Contact
Received on Monday, 25 October 2004 07:58:12 GMT

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