- From: Dave Reynolds <der@hplb.hpl.hp.com>
- Date: Fri, 08 Aug 2003 10:59:47 +0100
- To: Ian Horrocks <horrocks@cs.man.ac.uk>
- CC: Jim Hendler <hendler@cs.umd.edu>, public-webont-comments@w3.org
Ian, Many thanks for your response. These do seem like plausible reasons to be cautious and I can accept that the requirement is not strong enough to overcome that caution. So "this response is satisfactory". [Sorry for the slow reply, intervening holiday season.] Dave Ian Horrocks wrote: > > Dave, > > Thank you for your comments. > > I will attempt to provide some further clarification regarding the > WG's decision not to support naming of data ranges. The second part of > your comment (regarding bNodes) is/will be dealt with separately. > > The issue of named dataranges was discussed at the editors meeting in > Boston. (see [1]). The following potential problems were identified: > > 1. Clearly, we would like to have access in OWL to a full range of > user-defined XML Schema datatypes derived from the built-in datatypes > that can already be used in OWL (see [2]). This would include > enumerated datatypes corresponding to OWL dataranges. We expect > XML:Schema to ultimately provide a mechanism to support this. Naming > dataranges in OWL would provide a "competing" mechanism (i.e., > provide an alternative way to name user defined datatypes), and this > could interact in an undesirable way with the XML:Schema mechanism as > and when it is introduced. > > 2. OWL DL is designed so as to allow reasoning about datatypes and > values to be cleanly separated from reasoning about classes and > individuals. Introducing OWL names for dataranges may compromise this > design. > > It was therefore decided not to include them in the language at > present. It may be possible to add them in the future as and when a > thorough investigation of the issues proves that they would not have > any adverse effects. > > Please reply to this message as to whether this response is satisfactory, > copying public-webont-wg@w3.org. Again, thank you for your comments. > > Ian Horrocks > > On July 23, Dave Reynolds writes: > > > > Jim, > > > > Thank you for your response to the Jena team comments on these issues. > > Overall this response is not (yet) acceptable. > > > > (a) Issue: Named data ranges > > Your response: postpone > > > > We understand that the working group cannot name user-defined XSD datatypes > > and that matter should be raised with the XML Schema working group. > > > > Our concern was more one of uniformity - it seems possible to have both > > named and unnamed classes, why not data ranges? The more uniform a language > > is, the easier the API and the fewer the support calls. > > > > As an example could this: > > > > <owl:DataRange rdf:about="#MyDR"> > > <owl:oneOf> > > <rdf:List> > > <rdf:first>foo</rdf:first> > > <rdf:rest rdf:resource="&rdf;nil"/> > > </rdf:List> > > </owl:oneOf> > > </owl:DataRange> > > > > be included in OWL DL, for greater uniformity with other unnamed things in > > OWL DL (which can optionally be named). > > > > I confess to not understanding the research problems that you refer to as > > being raised by naming data ranges. If there is some non-trivial problem > > here then we certainly accept this is not a sufficiently important issue to > > warrant additional research at this stage in the process. > > > > Has the WG discussed this question? > > None of the three links you gave seemed directly related to our request: > > [1] > > http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.8-Datatypes > > [2] > > http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I4.3-Structured-Datatypes > > [3] > > http://lists.w3.org/Archives/Public/www-webont-wg/2002May/0040.html > > > > > > (b) Issue: bNodes as object in multiple triples > > Your response: no change due to lack of working group consensus > > > > The links you gave were all to the discussion before the last call. > > Please give an indication of the WG discussion of this issue in response > > to last call comments. > > > > Specifically you said: > > [[ > > The WG was concerned that the handling of blank nodes has not yet been > > shown to be able to be handled in the correspondence proof of Appendix A of > > the Semantic Document [6]. > > ]] > > However the following messages claim to provide such a proof: > > http://lists.w3.org/Archives/Public/www-webont-wg/2003Jun/0294 > > http://lists.w3.org/Archives/Public/www-webont-wg/2003Jun/0017 > > > > If this proof is indeed in error an analysis demonstrating the error could > > supply the test case that we requested. > > [[ > > A rationale for not permitting this in OWL DL > > should be given, preferably as a test case in OWL Full > > showing an OWL Full non-entailment that would hold in > > OWL DL if such triples were permitted. > > ]] > > > > > > (c) Issue: cycles of bNodes > > Your response: postpone > > > > Your follow up response was disappointing but acceptable. > > http://lists.w3.org/Archives/Public/public-webont-comments/2003Jul/0045 > > > > Dave, for the Jena team > > > > > > Jim Hendler wrote: > > > > > > Dave- > > > thanks for all the comments you raised on the > > > public-webont-comments@w3.org list. This is the response to the > > > remaining one: > > > > > > >This is a comment about blank nodes in OWL DL on behalf of the Jena team. > > > > > > > - We would like it to be possible to name dataranges > > > > > > The Web Ontology WG discussed this issue and others to do with naming > > > various datatypes under the issue "datatypes" which is issue 5.8 on > > > our issues list [1] and in our issue 4.3 of "structured datatypes" > > > [2], which included a discussion of naming datatranges raised by Ziv > > > Hellman [3] > > > Summarizing what can be seen in the discussions referenced there, the > > > WG felt that > > > (i) we should yield to RDF Core's decisions on datatyping, and > > > (ii)that we shouldn't create new URIs for datatypes that might > > > conflict with an eventual decision in the handling of XML Schema > > > Datatypes by the XML Schema group. > > > In light of these considerations, the group decided to postpone > > > issue 4.3 and not add named dataranges at this time. > > > The above assumes your question is specifically about complex > > > datatypes and ranges (i.e. being able to say a teenager has as age > > > property value between 13 and 19). Unamed datatranges could also be > > > asked about the ability to create datatypeProperties that are created > > > in a manner corresponding to the creation of unnamed > > > ObjecttypeProperties. This was not identified by the WG as a > > > requirement and raises some issues of a research nature as to the > > > handling of these within the DL restrictions. > > > > > > - It is natural in Jena to permit the java objects > > > representing blank nodes which > > > represent descriptions and restrictions to be > > > used more than once, and hence as the object of > > > more than one triple. > > > > > > A rationale for not permitting this in OWL DL > > > should be given, preferably as a test case in OWL Full > > > showing an OWL Full non-entailment that would hold in > > > OWL DL if such triples were permitted. > > > Below is an example such a test case, which we believe is an > > > OWL Full entailment. If on the contrary it were a > > > non-entailment, that would satisfy this comment. > > > > > > The issue of the proper treatment of blank nodes is a complex one, > > > and has received a great deal of discussion on the WG. Issue 5.26 > > > [4] involves many subissues involving the mapping between RDF and > > > OWL. Part of that discussion involved the treatment of blank nodes > > > similar to your discussion above. The group was unable to reach > > > consensus on this issue, and in fact ended up closing the issue over > > > the objection of Jeremy Carroll of Hewlett-Packard, his objection can > > > be seen in [5]. The WG was concerned that the handling of blank > > > nodes has not yet been shown to be able to be handled in the > > > correspondence proof of Appendix A of the Semantic Document [6]. > > > > > > - The RDF support within Jena permits users to: > > > - use annonymous nodes as the object of > > > more than one triple > > > - have cycles of anonymous nodes > > > While the syntactic restrictions between, for example, > > > unnamed individuals and descriptions are understandable, > > > it is not clear why OWL DL has not permitted, for example, > > > an unnamed individual to be the object of more than > > > one triple, or an unnamed individual to be the object > > > of a triple of which it is the subject. > > > Please either relax this constraint or offer a rationale. > > > > > > I am pasting in here the response that Peter Patel-Schneider sent to > > > another comment raising this same issue - his answer can be seen in > > > full in [7] > > > > > > The constraints on owl:equivalentClass triples can be articulated in terms > > > of Hamilton paths in the component graphs that are created by considering > > > only connected groups of blank nodes and named nodes that are connected to > > > these blank nodes. Neverthless, this is expensive to implement. > > > > > > The working group decided on 29 May 2003, as recorded in > > > http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0402.html, to > > > change the mapping for owl:equivalentClass from paths to connected graphs. > > > This should be much easier to implement. > > > > > > This change is reflected in the editor's draft of S&AS as of 30 May 2003, > > > which says: > > > > > > -------- > > > S: EquivalentClasses(description1 ˆÉ¬ÇˆÇ¬Ö descriptionn) > > > > > > T(S): T(descriptioni) owl:equivalentTo T(descriptionj) . > > > for all <i,j> in G where G is a set of pairs over > > > {1,...,n}x{1,...,n} that if interpreted as an undirected graph > > > forms a connected graph for -------- > > > > > > If you'd like to review this in context, you can take a look at the > > > editor's draft, in the the "Transformation to Triples" table at > > > http://www-db.research.bell-labs.com/user/pfps/owl/semantics/mapping.html > > > > > > I hope these responses will demonstrate the rationale behind the > > > decisions the WG has made on these issues. We hope you can accept > > > our postponement of one, reluctance to change our response on > > > another, and changes made to fix the third. > > > -Jim Hendler > > > for WOWG > > > > > > [1] http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.8-Datatypes > > > [2] > > > http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I4.3-Structured-Datatypes > > > [3] http://lists.w3.org/Archives/Public/www-webont-wg/2002May/0040.html > > > [4] > > > http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.26-OWLDLSyntax > > > [5] http://lists.w3.org/Archives/Public/www-webont-wg/2003Mar/0264.html > > > [6] > > > http://www.w3.org/TR/owl-semantics/proofs.html#A.1 > > > [7] > > > http://lists.w3.org/Archives/Public/public-webont-comments/2003Jun/0022.html > > > > > > -- > > > Professor James Hendler hendler@cs.umd.edu > > > Director, Semantic Web and Agent Technologies 301-405-2696 > > > Maryland Information and Network Dynamics Lab. 301-405-6707 (Fax) > > > Univ of Maryland, College Park, MD 20742 *** 240-277-3388 (Cell) > > > http://www.cs.umd.edu/users/hendler *** NOTE CHANGED CELL NUMBER *** > >
Received on Friday, 8 August 2003 06:01:10 UTC