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RE: [LC response] To Jeremy Carroll

From: Jeremy Carroll <jeremy@topquadrant.com>
Date: Thu, 2 Apr 2009 16:07:40 +0200
To: "'Ian Horrocks'" <ian.horrocks@comlab.ox.ac.uk>
Cc: <public-owl-comments@w3.org>
Message-ID: <000201c9b39c$697560a0$3c6021e0$@com>
> RDF interoperability: As we mentioned above, NF&R only covers new
> features. The motivation for RDF interoperability in OWL 2 is carried
> over from OWL 1 and is achieved via the same design principles--
> nothing has changed in this respect.

More time please
> Effective?: The abstract has been completely rewritten and no longer
> mentions effective reasoning algorithms.

Thank you

> Manchester Syntax: This is not a Last Call Working Draft, and the
> working group has decided that it will not be part of the
> recommendation but will be published as a working group note. It may
> be worth pointing out, however, that it is widely used, e.g., in
> TopBraid Composer, the Protege editor and the OWL 2 Primer.

More time please
> OWL/XML: It should be noted that RDF/XML is the only syntax that MUST
> be supported by implementations; support for the XML syntax is not
> required (see also FH3). The XML syntax is motivated by the desire to
> support OWL users who want better interoperability with XML based
> tools and languages, for example WSDL. An additional benefit is that
> XML data can be exposed to RDF/OWL applications using GRDDL (see
> [15]). We will extend NF&R to better motivate the need for an XML
> syntax.

More time please
> Links to Wiki should be links to TRs: Thank you for pointing this
> out. We will investigate the cause of the problem and ensure that it
> does not recur fix in future versions of the document(s).

> Syntax examples should include RDF: This deficiency has been noted
> and the current version of the Syntax document allows readers to see
> the RDF graph version of all examples.


> DisjointUnion subPropertyof UnionOf: You suggest "adding the
> assertion that owl:disjointUnionOf rdfs:subPropertyOf owl:unionOf".
> However, this doesn't make sense from a semantic point of view (see
> [17]).

I am surprised.
More time please.

> DisjointUnion and DisjointClasses: As you rightly say, these
> constructs do not extend the expressive power of the language, but
> only add "syntactic sugar". However, users of OWL have pointed out
> that the lack of such constructors is very inconvenient and can lead
> to a significant blow-up in the size of the ontology if large numbers
> of pair-wise disjointness axioms need to be added -- see, e.g., [3].
> The triple form of the new n-ary axioms and its relationship to the
> binary form exactly parallels the case for differentIndividuals, so
> it should not add significantly to the implementation burden.
> Implementers within the working group, including those working on
> triple-based implementations, do not consider these features
> difficult to implement.

More time please.

> Negative Property Assertions: Such assertions are useful in
> applications, e.g., to state that a person does not live at a given
> location or that their age is not a given value (see [5]). Using
> complements of hasValue restrictions is cumbersome, and it is hard to
> see how this would be easier for RDF based systems to process or how
> it would improve RDF interoperability. The OWL 2 RDF Based Semantics
> includes semantic conditions that deal with negated property
> assertions [6] and thus ensure interoperability.

This is not satisfactory.
The issue is that in some OWL syntaxes, proposed by the WG, the fairly large costs in terms of effective interoperability with RDF systems of negative property assertions as opposed to positive ones, is not apparent, except to the skilled user.

> SelfRestriction and the Schneider variant of the Patel-Schneider
> paradox: The ability to express additional "properties of
> properties", such as reflexivity, irreflexivity and asymmetry, is
> often needed in applications -- see, e.g., [7]. SelfRestriction
> provides for "localised" reflexivity. This may be more useful in
> practice that global reflexivity. 

More time please
> The OWL 2 RDF-Based semantics is
> not so susceptible to paradox problems, and so neither reflexivity
> nor SelfRestriction introduces any particular difficulties. NF&R
> discusses the support for this new feature.
Although I have not reviewed this document is detail, I believe this to be an improvement.

> QCRs: Thank you for your supportive comments.
> Reflexive, irreflexive, asymmetric and disjoint properties: see
> above. The usefulness of these features was explicitly mentioned by
> the Health Care and Life Sciences interest group in their last call
> comment -- see [13]. The Semantic Web Deployment (SWD) Working Group
> explicitly mentioned the usefulness of property disjointness for
> specifying the semantics for SKOS mapping relations, and the
> potential usefulness of reflexivity and asymmetry -- see [14].
> Reflexivity can also be used to "approximate" SelfRestriction in
> profiles that do not support this feature. NF&R discusses the support
> for these new features.

More time please

> Property chain inclusion axioms: At F2F5, the working group resolved
> to change the current RDF encoding of sub property chain axioms to a
> single triple form, which avoids the blank node on the left hand side
> and the use of "subPropertyOf" [4a]. The new vocabulary term
> "owl:propertyChainAxiom" has been introduced. Several documents were
> modified to effect this change - the best places to see the
> difference is in RDF-Based Semantics [4b], the Mapping to RDF was
> also changed [4c].

Sounds good, but I need more time (sorry) to review in detail.

> unary datatypes: Thank you for your supportive comments.
> N-ary datatype: Please see [10], where it says: "This specification
> currently does not define data ranges of arity more than one;
> however, by allowing for n-ary data ranges, the syntax of OWL 2
> provides a "hook" allowing implementations to introduce extensions
> such as comparisons and arithmetic." I.e., n-ary datatypes are not
> supported, but the language is designed so as to facilitate future
> extensions in this direction. Such an extension will be published as
> a working group note (currently under preparation -- see [16]).

Seems OK except for owl:real (see on)

> Annotations: We are glad to hear your general welcome for the
> improvements in the annotation system. Regarding the use of
> reification in annotations, this is mainly done in order to provide
> for annotations on axioms, a crucial feature in many tools and
> applications, as is suggested in your comment (note that this
> requirement was identified in the OWL Use Cases and Requirements
> document [2]). This is necessary, for example, on a simple subClassOf
> axiom relating two named classes; in this case there is no
> "convenient blank node", so your proposed solution does not work. In
> other cases, however, OWL 2 does attach annotations to blank nodes.
> RDF tools are accommodated in the existing design by including both
> "reified" and standard triple encodings of annotated axioms. The
> decision not to use RDF reification properties was taken in order to
> avoid overloading the meaning of the RDF vocabulary, and in response
> to comments from the RDF community (see Issue-67 [9]).

More time please.

> Profiles: Thank you for your generally supportive comments.
> Appendix and dependency on HCLS: As mentioned above, NF&R is only
> intended to provide examples that illustrate the rationale behind the
> new features of OWL 2. The HCLS community has been very energetic and
> has contributed many of these examples. We would welcome any examples
> that you might like to contribute from your user base to broaden the
> base of use cases in NF&R.
> UC#10 and UC#11: UC#10 and UC#11 motivate a feature which the working
> group was not able to fully develop, but for which it intends to
> publish a note [16]. It is true that these motivate a feature that
> did not ultimately become part of the language, although as we have
> discussed above the language does include the relevant "hooks" and an
> n-ary datatype extension will be published as a WG note [16].
> Moreover, documenting the motivation for unimplemented features may
> be of use to future working groups and is consistent with the
> approach taken in the OWL Use Cases and Requirements document [2].

Hmmm. More time on this one too.

> TopBraid Composer: This has now been corrected.

Thank you
> Trademark: This has now been corrected.

Thank you
> Error in Appendix and Informative?: We have deleted the reference to
> TBC in the IETF application. However, although support for Manchester
> syntax is optional, the working group still considers it worthwhile
> to continue with the mimetype registration.
> GRDDL: The working group has resolved to add GRDDL support to the OWL
> XML syntax (see [15]).
Thank you
> Informative?: See the above comment on OWL/XML. Although support for
> the XML syntax is optional, the working group still considers it
> worthwhile to continue with the MIME type registration. MIME type
> registration is not related to normativity.
[I am surprised by the last sentence]
More time (please)

> XSD datatypes: Some aspects of the OWL 2 use of XSD datatypes have
> been changed, in particular OWL 2 now makes the value spaces of all
> XSD primitive datatypes pairwise disjoint, as in XSD. Because of this
> change, owl:realPlus has been removed from OWL 2.
This seems good.

> owl:real: The new numeric datatypes specific to OWL 2 have been added
> partly to support reasoning with n-ary datatypes [16]. Unions of
> other datatypes are not adequate for this purpose.
If this is only for an experimental feature then it should be introduced with that feature and not in the main documents.
This datatype is very different from others, e.g. it is uncountable and has a non-surjective L2V.

> owl:datetime: This has been superseded by xsd:dateTimeStamp (see [12]).

Seems good.

> [1] http://www.w3.org/2007/OWL/wiki/New_Features_and_Rationale
> [2] http://www.w3.org/TR/webont-req/
> [3] http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0250.html
> [4a] http://www.w3.org/2007/OWL/meeting/2009-02-24#resolution_6
> [4b] http://www.w3.org/2007/OWL/wiki/index.php?title=RDF-
> Based_Semantics&diff=18494&oldid=18493
> [4c] http://www.w3.org/2007/OWL/wiki/Mapping_to_RDF_Graphs
> [5] http://www.w3.org/2007/OWL/wiki/
> New_Features_and_Rationale#F3:_NegativeObjectPropertyAssertion_Negative
> D
> ataPropertyAssertion
> [6] http://www.w3.org/2007/OWL/wiki/RDF-
> Based_Semantics#Semantic_Conditions_for_Negative_Property_Assertions
> [7] http://www.w3.org/2007/OWL/wiki/
> New_Features_and_Rationale#F6:_Reflexive.2C_Irreflexive.2C_Asymmetric
> [8] http://www.w3.org/TR/owl-xmlsyntax/
> [9] http://www.w3.org/2007/OWL/tracker/issues/67
> [10] http://www.w3.org/2007/OWL/wiki/Syntax#Data_Ranges
> [11] http://www.w3.org/2007/OWL/tracker/issues/97
> [12] http://www.w3.org/TR/xmlschema11-2/
> [13] http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/
> 0027.html
> [14] http://lists.w3.org/Archives/Public/public-swd-
> wg/2009Jan/0084.html
> [15] http://www.w3.org/2008/06/wiki_scribe/?source=http://www.w3.org/
> 2007/OWL/wiki/Chatlog_2009-02-24#resolution_16
> [16] http://www.w3.org/2007/OWL/wiki/
> Data_Range_Extension:_Linear_Equations
> [17] http://www.w3.org/2007/OWL/wiki/
> Direct_Semantics#Class_Expression_Axioms
> Please acknowledge receipt of this email to <mailto:public-owl-
> comments@w3.org> (replying to this email should suffice). In your
> acknowledgment please let us know whether or not you are satisfied
> with the working group's response to your comment.
> Regards,
> Ian Horrocks
> on behalf of the W3C OWL Working Group
Received on Thursday, 2 April 2009 14:08:34 GMT

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