- From: Pat Hayes <phayes@ihmc.us>
- Date: Tue, 27 Nov 2007 15:48:52 -0600
- To: "Michael Schneider" <schneid@fzi.de>
- Cc: "Owl Dev" <public-owl-dev@w3.org>, "Ian Horrocks" <horrocks@cs.man.ac.uk>, "Jeremy Carroll" <jjc@hpl.hp.com>, <bmotik@cs.man.ac.uk>
>[Comment to OWL-WG discussion; posted to involved WG-members] > >Hi, Ian and Jeremy! > >Just a small speculative comment on Jeremy's idea to use XML comments for >representing real semantic-free comments in OWL's RDF syntax: > >In > > http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0461.html > >Ian Horrocks answered to Jeremy Carroll: > >>> More constructively, what I am hearing, I think, is that the >>> requirement is for comments that have no semantics and just fit >>> into the specification in the right way. >>> >>> In RDF/XML there has always been the capability to have such >>> comments - they look like: >>> >>> <!-- >>> This is a comment, it has no bearing on the formal semantics of >>> the document. >>> --> >>> >>> It may be possible to provide say, an informative GRDDL transform >>> from an XML version of the axioms, to RDF/XML, and back again, that >>> round trips comments appropriately. >> >> As you probably recall, this was discussed and dismissed in the >> WebOnt working group for the reason that it is much too low-level (it >> is a feature of XML), and that such comments may be lost when >> documents are processed. What you propose w.r.t. GRDDL sounds more >> like a hack than a realistic solution. Moreover, this mechanism would >> hardly satisfy the requirement to have a more comprehensive framework >> that allowed (at least) for annotating axioms as well as entities. > >What comes to my mind is what's actually missing are "RDF comments", i.e. >comments which belong to an RDF graph, but which are not interpreted (all >triples within an RDF graph are always interpreted according to RDF >semantics). Webont/RDFWG discussed this idea. They were referred to as "dark triples", ie RDF triples which are not required to conform to the RDF semantics. (They have several other potential uses in addition to commenting: at one time it was thought that they were required to allow OWL to be encoded into RDF.) However, they raise many other issues, most importantly being how an RDF processor is supposed to be able to distinguish them from ordinary triples. To me, the most cogent argument against this idea is that it doesn't seem to actually be necessary. Suppose it were somehow arranged, and then someone accidentally thought that a dark triple were a real RDF triple. What harm would be done? Since RDF is so weak, I suggest that the answer is: no harm at all. The only thing that would follow from (be RDF-entailed by) such a dark/comment triple would be that the comment exists (i.e. the same triple with the comment replaced by a bnode); and since the comment is presumably a string, this seems a harmless entailment in any conceivable circumstance. >I am thinking about comments for URI resources, data values, >bNodes(?), whole triples, and possibly even subgraphs. To do subgraphs, it is necessary to somehow refer to or indicate the subgraph. This seems to require either a complete revision of the basic RDF graph model, or using named graphs. Ian's point above about axioms as well as entities is relevant here, of course. > This would make it >possible to really map both entity and axiom annotations in the Functional >Syntax to semantic-free comments in RDF. Of course, for every RDF >serialization language there would also have to be some specific >serialization for comments, but this would be an RDF issue, and would be >completely transparent to OWL. > >Well, as I said, this is a very speculative discussion, because there are no >such RDF comments at the moment, and so this does not help us any further in >the current situation. But should RDF get its own "RDF-1.1"-WG in some near >future, this might be a new feature to be considered. And then, perhaps, >already the next OWL-WG could use this new feature for creating a proper >RDF-mapping of real semantic-free comments (and perhaps deprecate the >annotation mapping which comes out from the current WG :-)). > >Ah, and please don't ask me about any technical details of such an RDF >comment feature! Well, but it might be worth thinking about it. It is rather a tar-pit. Is it *really* this important to avoid semantics? A commenting triple asserts... something (and that a character string exists, but we knew that already.) What, exactly, is not specified. So, is this really so dangerous that we need to revise the world to avoid it? Pat >All the comments in this post were just... speculative. ;-) > >Cheers, >Michael > >-- >Dipl.-Inform. Michael Schneider >FZI Forschungszentrum Informatik Karlsruhe >Abtl. Information Process Engineering (IPE) >Tel : +49-721-9654-726 >Fax : +49-721-9654-727 >Email: Michael.Schneider@fzi.de >Web : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555 > >FZI Forschungszentrum Informatik an der Universität Karlsruhe >Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe >Tel.: +49-721-9654-0, Fax: +49-721-9654-959 >Stiftung des bürgerlichen Rechts >Az: 14-0563.1 Regierungspräsidium Karlsruhe >Vorstand: Rüdiger Dillmann, Michael Flor, Jivka Ovtcharova, Rudi Studer >Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 cell phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
Received on Tuesday, 27 November 2007 21:49:15 UTC