[Pellet-users] minimal user-defined datatypes

[Henry S. Thompson]

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I've looked at all the information I can find in the archives wrt
user-defined datatypes, and can't find what I need -- I use a small
number of datatypes in my ontology, including NCName (defined by W3C
XML Schema, but not supported by pellet) and XPath (not defined by W3C
XML Schema).

I don't require any reasoning wrt these types, just to use them.

When I process my ontology, I get the following messages from pellet
(1.4RC2):

 Non OWL-DL features used:
  Unknown Datatype: http://www.w3.org/2001/XMLSchema#NCName is an
  unknown datatype
  Unknown Datatype: http://www.w3.org/2001/XMLSchema#XPath is an unknown
  datatype

 Add the following statements to make this document OWL DL
  <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" > 
    <rdf:Description rdf:about="http://www.w3.org/2001/XMLSchema#XPath">
      <rdf:type
  rdf:resource="http://www.w3.org/2000/01/rdf-schema#Datatype"/>
    </rdf:Description>
    <rdf:Description
  rdf:about="http://www.w3.org/2001/XMLSchema#NCName">
      <rdf:type
  rdf:resource="http://www.w3.org/2000/01/rdf-schema#Datatype"/>
    </rdf:Description>
  </rdf:RDF>
 
If I take that advice, the resulting ontology provokes a huge stream
of errors, beginning

 [Error] :5:26: s4s-elt-character: Non-whitespace characters are not
 allowed in schema elements other than 'xs:appinfo' and
 'xs:documentation'. Saw 'XML Schema'.

and ending

  WARN [main] (DatatypeReasoner.java:307) - WARNING: Cannot process
  the definition of the user-defined datatype
  http://www.w3.org/2001/XMLSchema#NCName

This is clearly happening because unqualified attempts to GET from the
XML Schema namespace URI retrieve an RDDL document, not a schema document.

Two questions:

 1) Is there any workaround possible for this, e.g. by telling pellet
    not to fetch the schema at all?

 2) Can pellet be fixed so that it either does its HTTP GET from
    namespace URIs using Accept: application/xml, so that it gets the
    schema document, or to interpret the RDDL and find the schema
    document pointer therein?

At the very least, the advice should be removed as long as following
it provokes an error. . .

ht
- -- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht at inf.ed.ac.uk
                   URL: http://www.ltg.ed.ac.uk/~ht/
[mail really from me _always_ has this .sig -- mail without it is forged spam]
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