- From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
- Date: Mon, 23 Jun 2003 14:47:51 +0100
- To: Jeremy Carroll <jjc@hplb.hpl.hp.com>
- CC: w3c-rdfcore-wg@w3.org
Jeremy Carroll wrote > I am not expressing a personal opinion on the content here. Having discussed this minute with Dave Reynolds, who leads on the Jena RDFS implementation, I now express what will pass for the HP opinion, which comes to a mild preference for the treatment in the current editors draft over the changes discussed in this minute. > 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) It seems like rather a big change to make at this late stage. Would you be confident there weren't other properties that need to be declared by fiat that haven't yet been identified? > > 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. > A further advantage is that it may make it less likely that someone will find an additional corner case like ter Horst's. > 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. This rules may be a nuisance but they are not a major obstacle. They don't look difficult or expensive to implement. Given that the result of the rewrite would be, in some sense, less clean I would think it would need some additional motivation than just moving a couple of obscure rules slightly further down in the appendix. Jeremy (with help from Dave Reynolds)
Received on Monday, 23 June 2003 09:48:21 UTC