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Teleconference.2008.04.30/Minutes
These minutes have been approved by the Working Group and are now protected from editing. (See IRC log of approval discussion.)
See also: IRC log
Contents
- Present
- Ian Horrocks, Boris Motik, Martin Dzbor, Peter Patel-Schneider, Bernardo Cuenca Grau, Carsten Lutz, Alan Ruttenberg, Uli Sattler, Jeremy Carroll, Ivan Herman, Ratnesh Sahay, Achille Fokoue, Michael Smith, Zhe Wu, Markus Krötzsch, Sandro Hawke, Diego Calvanese, Alan Ruttenberg
- Regrets
- Elisa Kendall (on travel), Evan Wallace (attending Interop. Week), Rinke Hoekstra (Queen's Day), Bijan Parsia (sick), Jie Bao (conflicts to other meetings), Michael Schneider (vacation)
- Chair
- Ian Horrocks
- Scribe
- Carsten Lutz
Admin
Ian Horrocks: roll call
Ian Horrocks: f2f3, my understanding is we agreed 28./29. July at MIT
Ian Horrocks: previous minutes
PROPOSED: to accept previous minutes
RESOLVED: accept previous minutes
Ian Horrocks: Strategy for putting up issues too complicated. New strategy: chairs look at them and decide whether they will be accepted
Pending Review Actions
Ian Horrocks: Action 140 and Action 141 (pending review) done
Overdue Actions
Ian Horrocks: Discussion of due Action 42, Action 129, Action 132 deferred since Bijan is not here
Ian Horrocks: Jeremy proposed to drop Action 135 (which was on him)
Ian Horrocks: Action 135 closed, Jeremy can create a new one later if necessary
Ian Horrocks: Action 43: Bijan suggested he might be able to help; come back next week
Jeremy Carroll: I would appreciate early feedback from others in the group on preliminary review that I will provide soon
Issues
Issue 82
Ian Horrocks: Issue 82 is really two issues; one is buggy diagrams which has been fixed by Boris and Conrad
Ian Horrocks: The second part is the general issue of what is going to happen w.r.t. OMG metamodel
Ian Horrocks: I propose to close issue as first part is solved and more concrete issues can be raised later when needed
Ian Horrocks: we talked to Evan and Elisa and Conrad and they were happy with this
PROPOSED: resolve Issue 82 as per the email
RESOLVED: Issue 82
Issue 107
Ian Horrocks: Regarding Issue 107, there is a proposal from Alan not to deprecate OWL Lite because there is no real need to do that
Alan Ruttenberg: Jeremy's advice should be somewhere in the documents
Jeremy Carroll: If we believe that people should think in terms of the new profiles and not of OWL lite, we should deprecate
Uli Sattler: we should be careful not to make OWL lite users think they have to change sth
Jeremy Carroll: agree with Uli in that the deprecation advice to OWL Lite users is "do nothing"
Ivan Herman: in other areas, deprecation means that, although it is still valid, in a later version we may make in invalid. Didn't find examples in W3C docs. But it has this aspect. Thus I am in favour of what Alan says
Jeremy Carroll: I am convinced by Ivans arguments
PROPOSED: resolve Issue 107 as per http://lists.w3.org/Archives/Public/public-owl-wg/2008Apr/0308.html
RESOLVED: Issue 107
Alan Ruttenberg: I will put Jeremy's comments as a note in the profiles document
ACTION: Alan to put editorial note in profiles document re: Jeremy's advise about OWL Lite
Issue 47
Ian Horrocks: Issue 47 is moot since compound keys are covered by easykeys
PROPOSED: Issue 47 resolved as addressed by EasyKeys
RESOLVED: Issue 47
Issue 122
Ian Horrocks: Issue 122 is already resolved; wasn't resolved when raised; but now resolved by the updates of the syntax and mapping documents after the F2F
Jeremy Carroll: I have heard that people don't like it, but not from HP so no problem here
PROPOSED: resolve Issue 122 as per http://lists.w3.org/Archives/Public/public-owl-wg/2008Apr/0334.html
RESOLVED: Issue 122
Issue Discussions
Ian Horrocks: Issue Discussions
Issue 71
Ian Horrocks: we reorder issues, start with Issue 71
Jeremy Carroll: the paper mentioned in the issue was maybe too complicated
Jeremy Carroll: there are linguist theries encoded in a language tag system in a bizarre fashion (?)
Jeremy Carroll: We need access to the language tag in the model theory, which is possible neither in OWL DL nor OWL Full
Jeremy Carroll: suggestion is to provide a property in OWL with a model-theoretic treatement that allows access to tags
Jeremy Carroll: different approach is to provide a way of creating data ranges of those plain literals that have language tags that are of a particular form: a rdf:type owl:PlainLiterals; a owl:withLanguageTag "en-US"^^xsd:language .
Ian Horrocks: a subclass of literals, like englishliterals?
Jeremy Carroll: yes; maybe we can do this using facets
Boris Motik: Interesting issue we may want to address. Two questions. First: for a bunch of objects, you have values connected via properties. If you want to single out all english literals, this can be done with facets
Boris Motik: That would allow to query all values in english
Boris Motik: Second question: do you really need to break down and get the actual language tag as a string?
Boris Motik: The latter would require n-ary datatypes
Jeremy Carroll: Refers to what is needed in the paper cited in issue description. Unions play an imporant way, e.g. for different versions of chinese
Peter Patel-Schneider: Patterns should work fine for language tags, XSD patterns
Ian Horrocks: why are literals not always a pair of language tag and content?
Jeremy Carroll: Describes decision made by RDF group, that plainliterals without lang tag are identical to xsd:string
Ian Horrocks: This could be the basis for a solution that Jeremy could write up
Alan Ruttenberg: I like the idea
Jeremy Carroll: I can write up sth that is likely to be consensus
Jeremy Carroll: Will write a wiki page with texts that could then go into the documents
Ivan Herman: It may be worth for Jeremy to talk to Felix Sasaki
ACTION: Jeremy, Start WIki page addressing lang tag issue, liasing with I18N activity (felix?)
Issue 97
Alan Ruttenberg: we were waiting for Ivan and Sandro to explain ramifications
Ian Horrocks: suggestion from Bijan was that we only need to provide some kind of hook
Alan Ruttenberg: We need an expert to help with that
Ivan Herman: my XSLT knowledge is not good enough
Ian Horrocks: the belief is that we really need to have it
Jeremy Carroll: we can send a message to the GRDDL WG and ask for volunteers
Ivan Herman: the GRDDL WG is hibernating
ACTION: Jeremy to send mail to GRDDL groups asking for volunteer (just in case)
Ian Horrocks: bijan is not here to argue that we do not need it; in the meantime, we can ping people to help us
Ivan Herman: according to GRDDL, the transformation is not necessarily in XSLT; but all known implementations are XSLT
Alan Ruttenberg: you can be conforming in that you return a generated XSLT; but we don't need a server that does the computation
Sandro Hawke: IMHO, this is cheating
Alan Ruttenberg: the server would be hosted at W3C
Sandro Hawke: bad if you are behind firewall
Ivan Herman: a GRDDL implementation might cache the transformation
Jeremy Carroll: I may not want to send my data over the internet to W3C
Issue 71
Jeremy Carroll: XHTML would be embedded as HTML, the lang proposal does not address XML Literals, in particular XHTML embedded in OWL
Ivan Herman: this is more relevant for RDF core than for OWL WG
Feedback on EasyKeys & Top/Bottom Role
Alan Ruttenberg: zhe, jeremy and achille; feedback on easykeys and top/bottomrole
Achille Fokoue: easykeys is fine with us; top/bottomproperty we don't really see strong concrete usecases; Markus sent feedback; I still have mixed feelings
Ian Horrocks: if you have implemented OWL DL, you have implemented top/bottomrole anyway in a certain sense
Ian Horrocks: so there is no implementation as such
Achille Fokoue: the question is whether we should encourage people to use that, and whether this will have performance impacts
Alan Ruttenberg: curious as well as to whether it is a performance issue
Uli Sattler: it's just syntactic sugar, no blowup
Uli Sattler: in practical cases, things may become a bit more tricky
Jeremy Carroll: our experience is that forward chaining itself is inadequate, and the right mixture of forward- and backward-chaining is the solution
Zhe Wu: no doubt that easykeys is practical; top/bottomrole people can represent it anyway so I have no strong feeling as long as we do not put a rule in OWL-R
Achille Fokoue: question is: potential impact on profiles
Ian Horrocks: it could just not be in the profile
Uli Sattler: the main motivation for having top/bottomrole was not urgent use cases; it was more to have a symmetric treatment of classes and properties
Uli Sattler: I do not think we should encourage people to use it a lot
Ian Horrocks: we should give people a bit more time to think about it
Alan Ruttenberg: I would say sth stronger; there are no objections, except some fear of performance impact, but it seems we are close to consensus to add those to OWL-DL
STRAW POLL: add top/bottomproperty to OWL-DL, take actions to check profiles
General Discussion: n-ary Datatypes
PROPOSED: http://www.w3.org/2007/OWL/wiki/N-ary_Data_predicate_proposal
Uli Sattler: explains current proposal
Carsten Lutz: Two confusing points in the proposal. 1. Value space is algebraic reals, should be reals. 2. In owl 1.0 strings are required, but the proposal does not make clear whether they would be required in OWL 2, whether the binary comparisons on them are required, and how exactly they would be interpreted.
Uli Sattler: have to recheck algebraic reals
Uli Sattler: as to facets, we just took the most obvious ones
Alan Ruttenberg: Asks for decidability when we put all things together
Uli Sattler: didn't we agree that this happens everywhere in OWL and we can live with it?
Alan Ruttenberg: this brings us out of OWL DL
Alan Ruttenberg: is the idea to have non-structural restrictions?
Carsten Lutz: As long as only the "required" datatypes and facets are used, no problem. Otherwise, the user is on his own. That's the only option.
Alan Ruttenberg: so we just say that: if you use optional and combine them, you are not guaranteed to be decidable
Ivan Herman: I am lost on how to express all that in RDF
Uli Sattler: one of the various issues we have to address if people like the proposal in general
Jeremy Carroll: how does the proposal constrain the interaction between these predicates and the XSD types
Uli Sattler: it doesn't constrain; as long as you use the required ones, you will be fine. When you use user-defined ones, it's your own responsibility
Jeremy Carroll: Is this proposal that we should encourage ontology designers to use mathematically more clean datatypes like real and integer, but not machine datatypes like byte and float?
Uli Sattler: yes
Michael Smith: bijan left RDF mapping open until there is support for the proposal by the group
PROPOSED: carry on with n-ary datatypes?
Jeremy Carroll: HP was very opposed; I can re-consult with colleagues to check; looks not that much better now
ACTION: Jeremy clarify HP position on n-ary datatypes
PROPOSED: should n-ary datatypes include optional datatype + predicates?
Alan Ruttenberg: a crucial point seems to be the RDF mapping