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A proposal for clarifying the definitions of datatype maps

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Thu, 30 Apr 2009 17:23:52 +0100
To: "'W3C OWL Working Group'" <public-owl-wg@w3.org>
Message-ID: <5FA361F1E09F48DBB9F5F08346DBA903@wolf>
Hello,

Michael pointed out in one of his review of conformance that the definitions of
datatypes might benefit from further clarification. In fact, I have noticed that
there is a slight inconsistency between the Syntax and the Conformance documents
regarding datatypes in OWL 2 DL. Conformance explicitly says that an OWL 2 DL
ontology must not contain datatypes other than the datatypes mentioned in the
OWL 2 datatype map; however, this is not reflected in the Syntax document, where
Section 5.2 implies that an OWL 2 DL ontology could include datatypes that are
not in the OWL 2 datatype map. As Conformance is more restrictive its conditions
on datatypes are the ones that actually hold.

I propose that we change the Syntax document to explicitly state this condition
on OWL 2 DL, i.e., the condition that an OWL 2 DL ontology must not contain
datatypes other than the datatypes mentioned in the OWL 2 datatype map. We could
then remove this condition from Conformance. This wouldn't involve any change to
the substance of the spec as a whole -- only to the form. I think that the
result would improve the overall clarity -- currently this important condition
relies entirely on a note in the conformance document.

At the same time, the Direct Semantics could be updated to clarify that the
datatype map D (used throughout the document) *must* coincide with the OWL 2
datatype map on the definition of the semantics of the datatypes from Section 4
of Syntax. Currently this rather important detail is nowhere explicitly stated.

Realizing these (editorial) changes would require the following modifications:

In Syntax:

- Clarify in Section 4 the distinction between "a datatype map" (i.e., a
container for some set of datatypes) and "the OWL 2 datatype map" (i.e., a
particular datatype map defined in the rest of the section).

- Remove any mention of datatype extensibility in Section 4.

- Change Section 5.2 to say that each datatype in an OWL 2 DL ontology MUST be
(i) in the OWL 2 datatype map, or (ii) rdfs:Literal, or (iii) not in the
reserved vocabulary of OWL 2. (Note that this last is to allow for user defined
datatypes.)

- Make the restriction in Section 5.7 on the well-formed literals pertain only
to OWL 2 DL (it currently pertains to OWL 2).

- In Section 11.2 replace "the datatype map" by "the OWL 2 datatype map" (as it
is used in an OWL 2 DL context here).

- In Section 11.2 remove the second condition on datatype definitions, as it is
now redundant.

- Adapt Section 3 to reflect all these changes.


In Conformance:

- Remove the last bit of 2.1.1 (the condition on datatypes in OWL 2 DL
ontologies), as would be included in Syntax.

- Remove Section 2.2, as it only restates information from Syntax, Direct
Semantics, and Profiles.


In Direct Semantics:

Clarify that the datatype map D (used throughout the document) must coincide
with the OWL 2 datatype map on the definition of the semantics of the datatypes
from Section 4.


Please let me know how you feel about this.

Regards,

	Boris
Received on Thursday, 30 April 2009 16:25:16 GMT

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