Re: reply to a POWDER Group request

Michael,

for the records, here is an updated answer draft. For the time being I
left the remark of referring to the OWL 2 Overview, I can remove that
item if the WG decides otherwise this evening. I have not made any
remark on XML Literals; as you say, that datatype is de facto part of
the OWL 2 RDF Based semantics, ie, the at-risk status would not affect
that. Finally, as I said the other day I would prefer not to comment on
their (informal) extension mechanism which is in line with what the
group does elsewhere.

Cheers and many thanks

Ivan

-------------------------------

Dear Phil,

thanks for you note. We have indeed found some problems in section 4.6
of http://www.w3.org/TR/2009/WD-powder-formal-20090403/ which needs
updates. There are as follows.

- The reference should be to XSD1.1 and not XSD2:
      http://www.w3.org/TR/xmlschema11-2/

- 'At the time of writing, the OWL-2' should say "OWL 2" (ie, no hyphen)

- The reference to OWL 2 currently points to the OWL 2 primer. We think
it would be better if it pointed at the (new) OWL 2 Overview document:
http://www.w3.org/TR/owl2-overview/

- The semantic condition refers to rdfs:Resource for the domain of
hasIRI. Although the description refers to an extension of the RDF
semantics, it makes use of, say, owl:DatatypeProperty. Hence it may be
stylistically better to refer to owl:Thing.

- The encoding of the condition in the example has several problems,
partially due to some recent changes in OWL 2. These are

    - namespace changes (OWL 2 refers to xsd:pattern directly and not
owl:pattern; it reuses rdfs:Datatype instead of datarange)

    - we also think that the type of restriction used is inappropriate.
owl:hasValue should refer to a single individual and not to a
datatype/datarange. Based on the rest of the POWDER semantics, what you
probably have to use is owl:allValuesFrom, but this is something you
have to decide, of course

    - the RDF mapping of facets is based on a list of blank nodes
instead of the approach used in the current code

The first example (the second has similar structure) should look
something like:

<owl:Restriction>
  <owl:onProperty rdf:resource="....#hasIRI"/>
  <owl:allValuesFrom>
    <rdfs:Datatype>
      <owl:onDatatype rdf:resource="...#string"/>
      <owl:withRestrictions rdf:parseType="Collection">
        <rdf:Description>
          <xsd:pattern rdf:datatype="...#string">PATTERN</xsd:pattern>
        </rdf:Description>
      </owl:withRestrictions>
    <rdfs:Datatype>
  </owl:allValuesFrom>
</owl:Restriction>


We are sorry not to have spotted this issue earlier.

Sincerely

Ivan
(In the name of the OWL 2 Working Group)



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Ivan Herman, W3C Semantic Web Activity Lead
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