- From: Bijan Parsia <bparsia@isr.umd.edu>
- Date: Thu, 17 Jul 2003 11:59:43 -0400
- To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
- Cc: public-webont-comments@w3.org
I'm satisfied by this response. Cheers, Bijan Parsia. On Thursday, July 17, 2003, at 11:47 AM, Peter F. Patel-Schneider wrote: >> Subject: Re: Semantics and Abstract Syntax (and some general OWL >> Lite, CR, & implementation) comments >> From: Bijan Parsia <bparsia@isr.umd.edu> >> To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com> >> Cc: public comments <public-webont-comments@w3.org> >> Date: Thu, 19 Jun 2003 14:49:16 -0400 >> >> On Friday, May 30, 2003, at 03:41 PM, Peter F. Patel-Schneider wrote: >> >>> This message responds to your comments, in each case not suggesting >>> any >>> changes to the S&AS document. This is not actually a rejection of >>> your >>> comments, however. I feel that you are generally satisfied with the >>> situation as it stands, but that some improvements could be made, if >>> possible. >> >> Yeeess. I think that's right. > > >>> One comment that you make corresponds to a re-opened issue that may >>> result >>> in a change - if this indeed happens we will let you know. >> >> Qualified cardinalities right? >> >> FWIW, I think this is a huge issue for many existing daml+oil users. I >> worry that people will just try to use the daml vocabulary with OWL, >> which seems icky. > > The Web Ontology working group reopened deliberations on qualified > cardinality restrictions, but on 8 May 2003 decided to postpone work on > qualified cardinality restrictions. The official information on this > postponement can be accessed at > > http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I3.2-Qualified- > Restrictions > > >>>> 1) Somewhat editorial: I think it would be invaluable for >>>> implementors, >>>> and even casual readers, to have the DLs that OWL Lite and OWL DL >>>> are >>>> notational variants of (mostly) explicitly mentioned (they are, >>>> respectively, to my best current knowledge, SHIF(D) and SHION(D)). >>> >>> Yes, the closest correspondences are to SHIF(D) and SHOIN(D), with >>> some >>> limitations on how datatypes are treated. >>> >>> It would be useful to have this somewhere. However, I don't think >>> that the >>> best place for this is in S&AS. >> >> I strongly disagree. S&AS is, in my opinion, reasoner implementors >> will >> go, especially those interested in implementing complete reasoners. >> That was my experience, and I lost a LOT of time trying to figure out >> how OWL lite was lighter than SHIF(D) (in a substantial way) and how >> that made anything easier. >> >> I would suggest that there be an "implementors note" break out box >> somewhere early in S&AS, prolly toward the end of the Abstract Syntax >> presentation. It could say something like: >> >> ***** >> IMPLEMENTORS' NOTE: OWL Lite and OWL DL closely correspond to the >> description logics known as SHIF(D) and SHION(D), with some limitation >> on how datatypes are treated. The abstract syntax for OWL Lite >> doesn't >> contain many of the common explicit constructors associated with >> SHIF(D), but the expressivity remains. >> ***** >> >>> If you have a suggestion for a suitable >>> place to stick this information, let us know. (If the wording fits >>> nicely >>> in S&AS, it might even make it in there.) >> >> I actually can't think of a better place to put it. > > This has been added as a Note just before Section 2.1. To see the > change > look in > http://www-db.research.bell-labs.com/user/pfps/owl/semantics/ > >> [snip] >>>> I mean, given that OWL Lite can express general inclusion >>>> axioms, what exactly does it help to have the restrictions on the >>>> left >>>> hand sides of the various axioms? The syntactic restrictions seem to >>>> only be of interest at the authoring or serialization level. >>> >>> The simpler axiom forms are intended to be reminiscent of frame >>> systems. >>> Most people write ontologies using mostly these forms, so it was >>> decided to >>> provide a syntax slanted towards them. Some of this is already >>> covered in >>> Guide. >> >> That explains why in the *concrete* syntax, but not in the *abstract* >> syntax. I.e., why not >> represent multiple subclassings as the subclass of an intersection (in >> the abstract syntax)? >> >> I mean, I could imagine that it would complicate the mapping to >> triples, but I don't see off hand. >> >> Are ANY users (as opposed to implementors) going to look at the >> abstract syntax, or S&AS for that matter? If so, I would suggest that >> S&AS should be made convenient for implementors, not end users. That >> you have to use natural language to explain something that could >> easily >> be directly expressed in the abstract syntax makes the abstract syntax >> a bit less useful. > > This is a question that will most likely be answered by developers of > OWL-related systems that include user interfaces. It is probably > easier > for implementors of such systems to internally use a syntax that is > close > to syntax that they present to users, and the abstract syntax might be > such > a syntax. > >>>> Similarly, even we have somewhat explicit intersections (from the >>>> text), but nothing saying "intersectionOf" in the syntax. Ok, I >>>> suspect >>>> this makes the mapping to triples easier, but it makes understanding >>>> the language from the implementation point of view much more >>>> difficult. >>> >>> The tradeoffs in the syntax of OWL Lite are somewhat unusual. The >>> syntax >>> of OWL Lite is supposed to be similar to frame syntax, thus the lack >>> of >>> explicit intersectionOf. I agree that from the logical point of view >>> there >>> is no reason for this, but it is supposed to be easier to write and >>> to >>> parse. >> >> Right, and that's fine for OWL lite, but it doesn't explain bubbling >> up >> these restrictions to the Abstract syntax level. > > It is part of the design criteria of the abstract syntax to > > facilitate[] access to and evaluation of the language. This > particular syntax has a frame-like style, where a collection of > information about a class or property is given in one large > syntactic construct, instead of being divided into a number of > atomic chunks ... [Section 2 of S&AS] > > which indicates that a more accessible syntax is better even though > that > might somewhat obscure the actual expressive power of the language. > >>> There are short allusions to this in various places - a long allusion >>> would be quite lengthy and probably not suitable. >> >> I would accept language along the lines I gave above. My favored >> solution would be a more explicit abstract syntax, but that's probably >> too much work. But then there *really* needs to be a blocker of the >> misunderstandings that in my own experience, and from that of my >> students, are far too easy to make. > > The statement of correspondence between OWL Lite and SHIF(D) should > help > here. > >> [snip] >>>> *************** >>>> 2) Completely Editorial: I would like the normative version of the >>>> document to be a single HTML file. I know, off hand, of no other (at >>>> least modern) W3C recommendation that is split up merely for >>>> navigational purposes. It's inconvenient, it's inconsistent even >>>> with >>>> the other OWL specs, and annoying, especially for offline reading. >>> >>> I agree somewhat, but do find the separated version to be helpful >>> sometimes. I was asked to make the switch from a single to a >>> compound >>> document, and I'm not particularly interested in switching back. >> >> Er...but none of the other documents, afaik, either in webont or >> rdfcore are compound. Few if any, again afaik, modern W3C recs are >> compound. I would have thought that that would be determinative :) > > OWL Test Cases is a compound document. > >> Not a biggy, but it does annoy me each and every time. And I often >> forget that it's compound and thus load up only the first page and >> find >> myself off line with not what I wanted. Oh well. Bookmarking the >> single >> file will work. But I predict other people's annoyance. >> [snip] > > No change is likely to be made here. > > >>> Please respond, copying public-webont-comments@w3.org, as to whether >>> you >>> are satisfied with this response, whether you need to wait until >>> certain >>> changes to the design of OWL are done, or whether further >>> correspondence is >>> needed now. >> >> CardinalityQ: need to wait > > OFFICIALLY POSTPONED, see above. > >> Adding "Implementors' note": I will be satisfied if something like >> this >> is added. I won't be if not. I think >> S&AS is exactly the right place for this information and it doesn't >> seem like a large change. > > DONE, see above. > >> Single HTML file: Looking at: http://www.w3.org/2001/06/manual/#Large, >> I'm not convinced that S&AS is actually "large" enough to count as a >> large one. It certainly doesn't need compression to facilitate >> download >> in most circumstances. But I guess if it is "large", then as long as >> the >> other advice is followed, I can't strongly object. I might then object >> that similarly long documents *aren't* broken up. > > NOT DONE, but as you say, it is possible to easily access the combined > document. > >> Cheers, >> Bijan Parsia. > > Please reply to public-webont-comments@w3.org as to whether you are > satisfied. > > Thanks for your continuing comments. > > Peter F. Patel-Schneider > Bell Labs Research
Received on Thursday, 17 July 2003 11:58:56 UTC