- From: Dan Brickley <danbri@w3.org>
- Date: Fri, 21 Mar 2003 09:47:43 -0500
- To: Vassilis Christophides <christop@ics.forth.gr>
- Cc: brian_mcbride@hp.com, www-rdf-comments@w3.org
Hi * Vassilis Christophides <christop@ics.forth.gr> [2003-03-21 16:11+0200] > Dan > > I have argue several times about the RDF Schema issues presented in > summary in my mail. Yes, as Pat noted these are topics that have also taken up a fair amount of time in the RDF Core and WebOnt WGs, as well as the DAML+OIL work that preceded WebOnt, and in the RDF Interest Group. > No I am not satisfied by Pat Hayes answer. My problem is that I don't > have enough time to debate with excaustive details. I appreciate the time problem. At this stage in the RDF Core work, we would however need to assemble a pretty compelling case that the current design is broken. I believe everyone agrees that there are other ways that RDF could have been designed, and that there are costs and benefits associated with each design. At this stage I am focussed solely on making sure that critiques of RDF Schema presented during Last Call get acknowledged and handled by the working group. I think the best thing to do is open a Last Call RDFCore WG issue and have the working group consider your concerns, as expressed here, in the original message, and in the papers you cite. I am trying to break your comments down into issues we could productively discuss. Two of your key concerns are: -rdf/s layering too flat -property instances aren't explicitly represented You also present an alternate design for domain and range, a design which has been considered at length and ultimately rejected by the RDF Core (and WebOnt) working groups. Similarly, you express a preference for the older (and previously rejected by both WGs) design that banned rdfs:subClassOf cycles. I could request issues be opened for these, but in the absence of compelling new evidence, I would not expect the WG to seriously consider changing its design. I won't deal here with your comments on datatyping; someone else will (or has) respond to that. I propose we focus on your two concerns that have not been so explicitly discussed by the WG: layering and property instances. Shall we request the WG open issues for the 'layering is too flat' and 'property instantiation' concerns that you raise? > The axis of critic > are: > > 1) Some of the RDF/S features are not justified by real application > needs (at least the 2-3 applications I am dealing with) Other's experience seems to differ. We need to finalise on a single design so at this stage, if you are asking for a major redesign, we need evidence of major problems. In my experience, rdfs:subClassOf, and the associated simple extensional semantics associated with it, is very well suited to mixed- namespace, open world Web applications. In a more closed environment I share your preference for avoiding subclass loops. RDFS, however is a language designed for deployment in the Web. > 2) They imply serious implementation limitations > > For example, class cycles is a very confusing notion in P2P e-learning > applications, developers can't skip off this costly reasoning since it > is embedded in the default RDF/S Semantics and there no efficient > algorithms to implement transitive closure computations. > > More than an official response, I need a fruitful scientific > discussion on these issues. We at least trying to explain our > objections in all our papers > (http://139.91.183.30:9090/RDF/publications/FuncBook.pdf > http://139.91.183.30:9090/RDF/publications/comp-networks2003.pdf) I want to make sure the Working Group are aware of your concerns, review comments, and alternate designs. At this stage the best way to do that is to focus on specific issues that, given the stage we're at (post Last Call) will have most chance of improving the RDF specifications. Revisiting subClassOf and domain/range discussions of 1998-2002 is unlikely to be productive unless new evidence is brought to bear. All viewpoints on this (including logical, application-oriented, tool developer etc) have been thoroughly aired, on www-rdf-comments, www-rdf-interest, www-rdf-logic, and elsewhere. The working group membership have studied much of this material, participated in those debates, and the result was the design published as our Last Call specs. I'm concerned that we take time now to distinguish any new points you're raising from design discussions which (in my opinion) have been exhausted and full examined. In that light, I'm proposing that the WG open issues for the 'flat layering' and 'property instances' concerns you raise above. I hope my comments don't appear dismissive. My understanding is that your views were taken into account during the discussions of the last few years, even if the final specifications did not match the design you would have preferred. Let me know whether you would like me to proceed with the two issues above. Thanks again for your review, cheers, Dan
Received on Friday, 21 March 2003 09:47:51 UTC