- From: Jos De_Roo <jos.deroo@agfa.com>
- Date: Sat, 21 Jun 2003 00:45:40 +0200
- To: "Jeremy Carroll <jjc" <jjc@hpl.hp.com>
- Cc: w3c-rdfcore-wg@w3.org
This is a very nice and important report. I now better understand the arguments and agree that rules rdfs12a and rdfs12b look bizarre (but are easy to implement) and would agree to move them to the place of rdfs2a rdfs3a rdfs4a' and rdfs4b' (which are indeed causing a combinatorial explosion, at least rdfs2a rdfs3a + owl) -- Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/ Jeremy Carroll <jjc@hpl.hp.com> To: w3c-rdfcore-wg@w3.org Sent by: cc: w3c-rdfcore-wg-requ Subject: horst-01 - after hours discussion est@w3.org 2003-06-20 07:25 PM This is a *scribe* report on the after hours discussion. I am not expressing a personal opinion on the content here. After hours of telecon today, the determined few (I think DanC, PatH, Jeremy, JanG, DanBri) kept going for longer, discussing the complexity of the 12a and 12b rules added to address horst-01 (one of the AOB items!). A different possible design (to that in the editor's draft) was discussed. The current design has extensional definitions of subClassOf and subPropertyOf. http://www.ihmc.us/users/phayes/RDF_Semant_Edit_appenda.html#rdfs_interp [[ <x,y> is in IEXT(I(rdfs:subClassOf)) if and only if x and y are in IC and ICEXT(x) is a subset of ICEXT(y) <x,y> is in IEXT(I(rdfs:subPropertyOf)) if and only if x and y are in IP and IEXT(x) is a subset of IEXT(y) ]] This could be changed to intensional definitions [[ If <x,y> is in IEXT(I(rdfs:subClassOf)) then x and y are in IC and ICEXT(x) is a subset of ICEXT(y) If <x,y> is in IEXT(I(rdfs:subPropertyOf))then x and y are in IP and IEXT(x) is a subset of IEXT(y) ]] transitivity and reflexivity can be achieved by fiat: e.g. [[ IEXT(I(rdfs:subClassOf)) and IEXT(I(rdfs:subPropertyOf)) are transitive and reflexive. ]] (in the green box) There was discussion of whether it is useful to have rdfs:Resource as the maximal class. If yes, then this too, would have to be declared by fiat in the model theory. It was suggested by Pat that declaring conditions by fiat was distasteful. (Note the current truth of transitivity, reflexivity and rdfs:Resource as maximal all follow from the extensional reading of rdfs:subClassOf - thus any of these features we wish to maintain has to be explicitly added to the MT). The section 4.1 http://www.ihmc.us/users/phayes/RDF_Semant_Edit_appenda.html#ExtensionalDomR ang would be retitled, to "Extensional RDFS" or something like that, and permit semantic extensions to add back in the extensional reading of subClassOf and subPropertyOf. ==== The rationale for such a change comes in the entailment rule appendix. The bizarre rules rdfs12a and rdfs12b would no longer be needed, since their validity depends on the extensional reading of subClassOf. They would hence be moved from the main RDFS section to the variant at the end (with rdfs2a rdfs3a rdfs4a' and rdfs4b'). Moreover, the completeness fix I noted in my review would then be added to the only occurrence of these rules. Since these rules are a significant obstacle to complete implementation of RDFS, dropping them to the optional extras section, is an advantage. Jeremy (I believe that Pat and Dan were the only others left, when we decided to minute the after hours discussion).
Received on Friday, 20 June 2003 18:45:58 UTC