- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Wed, 30 Jul 2003 07:52:46 -0400 (EDT)
- To: phayes@ihmc.us
- Cc: w3c-rdfcore-wg@w3.org, www-rdf-comments@w3.org
From: pat hayes <phayes@ihmc.us> Subject: Re: semantics update Date: Wed, 30 Jul 2003 01:24:15 -0500 > >From: pat hayes <phayes@ihmc.us> > >Subject: semantics update > >Date: Mon, 28 Jul 2003 23:29:18 -0500 > > > > > http://www.ihmc.us/users/phayes/RDF_Semant_Edit_Weak.html > >> > >> now reflects the post-Beckett/PFPS/Carroll editing and all subsequent > >> decisions. It has a slightly different look/feel (colors, table > >> titles etc) , updated references (though if anyone has any complaints > >> about any of those please feel free to correct me) and some more > >> anchors and internal links. Ive made the text links slightly visible > >> by messing with the background color, but if people don't like this > >> its easy to tweak it in some other way. > >> > >> Text changes since the last version are in red. They include > >> rewriting of the definition of 'merge', some minor rewordings to > >> clarify meanings more carefully, and putting back the definition of > >> 'vocabulary entailment' which had gotten lost somewhere (its now > >> section 2.1 and has several links to it) and references to blank node > >> *identifiers* in the statement of the rules (suggested by Dave). Also > >> the dire warning about rdf:value (section 3.2.4) has been made less > >> dire, also suggested by Dave. > >> > >> Significant changes are that XMLiteral values are stated explicitly > >> to be distinct from character strings (defn of RDF interpretation, > >> section 3), and the equivalence between plain literals and xsd:string > >> typed literals is noted explicitly and an inference rule provided > >> (end of section 7.4). The wording of the Lbase translation has been > >> slightly altered to fit that last change also. > >> > >> The change list has been rewritten and is at the end. > >> > >> Pat > >> > >> PS. Peter, I believe this now addresses all your concerns. > > > >It may be that the changes do address all my concerns, I don't have time to > >check just now, and may not for at least a week. > > > > > >However, during the quick check I just made I found some remaining > >concerns. The first thing I checked was the list of post-last-call > >changes. I noticed that several changes that result in changes to RDF(S) > >entailments are not mentioned as substantial changes. > > > >The change making LV = ICEXT(I(rdfs:Literal)) means that > > ex:foo ex:rel "a" . > >rdfs-entails > > ex:foo ex:rel _:x . > > _:x rdf:type rdfs:Literal . > >whereas it does not in the last call semantics. This was pointed out in > >http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0085.html. > > > >The change to datatyping in RDF makes many changes to D-entailments. In > >the last call semantics, there were few D-entailments, as there was no way > >to impose connections between typed literals and datatypes. For example, > > ex:foo ex:rel "1"^^xsd:decimal . > >did not xsd-entail > > ex:foo ex:rel "01"^^xsd:decimal . > >in the last call semantics because xsd-interpretations did not require that > >I(xsd:decimal) be the xsd:decimal datatype. > > I view both of these as ERRORS in the last call document which have > now been fixed, in both cases in close consultation with you, for > which I am grateful. So I am not sure what your point is here. Are > you saying that you want us to revert to the situation in the LC doc? Of course not. However, I believe that they need to be documented as changes that could be seen by users. > >The change requiring non-emtpy datatypes, although it technically does not > >affect any entailments, changes the permissable set of RDF datatypes, and > >thus forms a significant change to the RDF datatyping design. > > Do you , honestly now, think of this as a SIGNIFICANT change? Can you > cite any example that has been seriously proposed of a datatype with > empty domains? Again, I regard the omission of this condition simply > as an editorial oversight: frankly, I never even thought about the > possibility of an empty dataype until you pointed out that it was not > explicitly prohibited and, if ever defined, would produce strange > behavior in the semantics. So I prohibited it. Again, this is a change to the specification that impacts its users. I believe that it thus needs to be documented as a change. > >Without a comprehensive list of such changes, I do not view the RDF > >Semantics document as complete. > > > > > >Problems arise in the description of other changes. I can't > >imagine how the significant changes to the mapping to Lbase can be listed > >under ``The following changes do not effect [sic] the technical content.'' > > Perhaps that could be better phrased. I should have said 'normative > technical content' > > >The change to lists doesn't affect any entailments that I can see. In > >fact, the it doesn't change anything at all with respect to the semantics, > >even the set of RDF graphs that are the result of RDF/XML parsing. > > That is true, I should have listed that in the previous section. > > >The change to datatypes is not needed for compatability with OWL. It is > >instead needed because the last-call treatment of datatypes didn't work > >right. > > > It was the need to support OWL identity reasoning which brought this > to the fore, but OK. I disagree even with this claim. Before the changes to datatypes, there were expected D-entailments that just didn't follow. Perhaps OWL depended more on these changes being made, but I would hope that the changes were made to fix the problems with D-entailments, not just to support OWL identity reasoning. > >Peter F. Patel-Schneider > >Bell Labs Research > >Lucent Technologies > > > > > >PS: I also noticed a typo in 4.3 - Rdf -> Rdfs > > thanks. > > OK, the version at my URI now has the change list rephrased more in > line with your remarks above (and the typo fixed). Textual changes > marked in red; some of the material has been moved to other headings > also. Apart from the typo, the main text is unaltered. > > Pat peter
Received on Wednesday, 30 July 2003 07:52:55 UTC