ISSUE-157 Draft response [was Re: OWL WG LC comment for SKOS reference document]

All,

This is a *draft response* wrt ISSUE-157. Please send comments 
to the list. As agreed during the last telecon, we intend to 
send the actual response Friday 5 Dec, end of the day, so 
reactions before that time would be very much appreciated.

Guus


-----------------------
Peter,

Thanks again for your comments on behalf of the OWL WG [1]. This 
is a response to part of these comments, marked in our issues 
list as ISSUE-157 "SKOS and OWL 2 analysis" [2]:

[[
   The OWL WG notes that some parts of the SKOS specification 
and some examples in the reference document do not fit within 
OWL 2 DL and that thus may not be fully supported by Semantic 
Web tools.  The OWL WG presents the following analysis of the 
SKOS specification and examples, to indicate where 
representation capabilities beyond OWL 1 DL are used. The OWL WG 
further notes that in many cases the SKOS specification fits 
within OWL 2 DL, but that the examples do not.  The OWL WG 
suggests removing those examples that do not fit within OWL 2 
DL.([from [1])
]]

below you find our responses to the SKOS aspects that are not 
OWL 2 DL compliant. As a general strategy, we have tried as much 
as possible to accommodate the alignment with OWL 2 DL. A number 
of specific points cannot be resolved at this time (see below), 
so we have decided to POSTPONE this issue.

[[
Section: Lexical Labels
Language: OWL 2 Full
Issue: subproperty of rdfs:label
Suggestion: don't use rdfs:label
]]

We prefer to keep the subProperty relation; however, we propose 
to change the type of the lexical label to 
owl:AnnotationProperty. Assuming that OWL 2 DL will support 
subproperty statements between annotation properties, this 
change shroud at least partially solve the issue.

[[
Section: Lexical Labels
Language: OWL 2 Full
Issue: objects as values of data property (example)
Suggestion: don't do this
]]

We assume you refer to example 17; we propose to remove this 
example.

[[
Section: Documentation
Language: OWL 2 Full
Issue: using literal in object property (examples)
Suggestion: don't do this

Section: Documentation
Language: OWL 2 Full
Issue: use of rdf:value (example)
Suggestion: don't use rdf:value
]]

We assume you refer to examples 24,25 and 27. We propose the 
following changes:

- move examples 24 and 25 to Sec. 7.5.2., i.e. the note on 
alignment of the range semantics with OWL semantics; this would 
leave only the "OWL 2 DL"-consistent example in Sec. 7.4;

- change example 27 to use as subject a resource with an 
rdf:value property;

- reverse the order of the two notes, i.e. Sec. 7.5.1. and Sec. 
7.5.2.

We prefer to keep the rdf:value examples, as this the RDF 
standard defines this as the preferred way of identifying the 
value in "value" resources. However, these rdf;Value are now 
only used in "Note" sections, which contain the appropriate 
caveats about the semantics.

[[
Section: Lexical Labels
Language: not OWL
Issue: axiom schema for unique prefLabel
Suggestion: include qualified cardinality restrictions only
   for languages used (defined using datatype restrictions)

Section: Concept Collections
Language: OWL 2 Full
Issue: ordering with typing
Suggestion: see [1]

Section: SKOS XL
Language: OWL 2 Full
Issue: data property chains
Suggestion: ??
]]

We assume these three issues refer to constraints S14 (lexical 
labels), S35 (ordered collections) and S56, S57 & S58 (SKOS XL). 
Indeed, these constraints can (currently) not be expressed in 
OWL. However, these are useful constraints for tool developers 
and we therefore prefer to keep these in the SKOS Reference.


Please let us know whether you can live with this response.

Thanks again for your comments!

Regards,
Guus

[1] 
http://lists.w3.org/Archives/Public/public-swd-wg/2008Oct/0059.html
[2] http://www.w3.org/2006/07/SWD/track/issues/157