[Pellet-users] minimal user-defined datatypes

[Evren Sirin]

On 3/11/07 11:35 AM, Henry S. Thompson wrote:
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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?
>   
The behavior to automatically fetch and load XML schemas has been 
disabled recently (in the SVN) as the preferred method of defining 
user-defined datatypes is inlining as described in the OWL 1.1 spec. An 
option has been added for those who still would like to load XML schemas 
which can be turned on by setting PelletOptions.AUTO_XML_SCHEMA_LOADING 
to true. The final release of version 1.4 whihc includes this addition 
will be ready to download before the end of this week so you might just 
update then and this problem should go away.
>  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?
>   
Yes, that would be a nice good addition. But as we are moving away from 
loading XML schema documents anyway I don't think we will be adding this 
feature.

Cheers,
Evren
> 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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