- From: David Booth <david@dbooth.org>
- Date: Sun, 04 Aug 2013 17:07:59 -0400
- To: Sandro Hawke <sandro@w3.org>
- CC: Pat Hayes <phayes@ihmc.us>, David Wood <david@3roundstones.com>, public-rdf-comments <public-rdf-comments@w3.org>
I would be okay in principle with including the definition somewhere with appropriate warning, but since the exact wording and context is so critical to its interpretation and impact, I would have to see the final verbiage to say for certain. I do agree that the notion of "generalized RDF" is useful, but I don't think the W3C should encourage or promote its use. I think the most appropriate place for the definition of "generalized RDF" would be in the RDF Semantics document, for two reasons: (a) that's where the notion is actually used (to simplify entailment rules); and (b) that would give it less prominence and hence reduce the likelihood that someone would think it is a form of standard RDF. David On 08/04/2013 07:57 AM, Sandro Hawke wrote: > > > Pat Hayes <phayes@ihmc.us> wrote: >> The terminology is already out there, eg >> http://www.w3.org/TR/owl2-profiles/ is a Rec from 2012 which >> defines and uses the idea (see >> http://www.w3.org/TR/owl2-profiles/#Reasoning_in_OWL_2_RL_and_RDF_Graphs_using_Rules), >> >> and http://www.w3.org/TR/rif-rdf-owl/ is a 2013 Rec which has been a >> Candidate Rec since 2009 > > Actually a REC since 2009. Otherwise I agree with all this. :-) > Hopefully we can add a little text to RDF Concepts so others > understand this before starting a thread on the comments list. > Assuming that text is okay, would you be satisfied, David Booth? > > - Sandro > > also defines and uses it. (see >> http://www.w3.org/TR/rif-rdf-owl/#Syntax_of_RIF-RDF_Combinations ). >> The second one also has this in its "end note" (my emphasis >> added): >> >> "Generalized RDF graphs: Standard RDF graphs, as defined in >> [RDF-Concepts], do not allow the use of literals in subject and >> predicate positions and blank nodes in predicate positions. The >> RDF Core working group has listed two issues questioning the >> restrictions that literals may not occur in subject and blank nodes >> may not occur in predicate positions in triples. ***Anticipating >> lifting of these restrictions in a possible future version of >> RDF***, we use the more liberal notion of generalized RDF graph. We >> note that the definitions of interpretations, models, and >> entailment in the RDF Semantics document [RDF-Semantics] also apply >> to such generalized RDF graphs." >> >> Apparently their anticipation was misguided, but I can attest that >> almost any expressive extension of RDF would be easier and more >> naturally defined on generalized RDF than standard RDF, regardless >> of its lack of normativity. So it *will* get used. I don't think we >> should discourage or encourage, just state the facts about what is >> normative. Discouraging the use of generalized RDF amounts to >> discouraging the use of RIF and OWL2 and JSON-LD and discouraging >> the use of complete RDF reasoners, among other foolish things to >> try to discourage. We are in the minority on this issue. >> >> I think DavidB's concerns might be alleviated if we could call it >> by a different name, because "generalized RDF" does sound like a >> kind of RDF. But this name is already in use, so to change it now >> might cause more confusion. As usual, writing standards is a >> lose/lose situation. >> >> Pat >> >> >> On Aug 2, 2013, at 8:22 AM, David Wood wrote: >> >>> Yes, I concur with Sandro. The RDF WG inserted the "generalized >>> RDF" >> description for a good reason. It is there to allow for alignment >> with JSON-LD and any future implementations or formats that cannot, >> for good technical reasons, limit their possible parsings to >> standard RDF. >>> >>> That does not mean, however, that we should encourage >>> "generalized >> RDF" at any point. Its use should be strongly discouraged in >> implementations and where that is impossible, as with JSON-LD, then >> its /social/ use should be strongly discouraged, as with JSON-LD. >> Hence, I think we should put in the stronger wording but leave the >> concept in place. >>> >>> Chair and editor hats simultaneously "on" and "off". Take that, >> Erwin Schrödinger! >>> >>> Regards, Dave -- http://about.me/david_wood >>> >>> >>> >>> On Aug 2, 2013, at 09:15, Sandro Hawke <sandro@w3.org> wrote: >>> >>>> Speaking just for myself, I think this is going too far. I >>>> think >> it does a service to the community to define the term "generalized >> RDF" in RDF concepts, since (1) it's used in at least two of our >> specs which we'd rather not have depend on each other (JSON-LD and >> RDF Semantics), and (2) it's something people come up with on their >> own anyway, and this way we tag the discussions about it. It's >> hard to evolve or extend a standard interchange format, but the >> best hope for doing so is to have everyone who wants to add some >> feature add it in the same way and talk about it the same way. By >> defining "generalized RDF" in RDF Concepts, I think we're doing >> that. >>>> >>>> All that said, I think it would be a good idea to add something >>>> like >> the warning note you propose, and perhaps some of the explanation >> I just provided. That is, roughly: Generalized RDF is not >> standard RDF, but it can be useful and is reasonable to use among >> systems which have all agreed to use it. If you try to send it to >> systems which have not agreed to use it, it won't work. >>>> >>>> -- Sandro >>>> >>>> On 08/01/2013 04:17 PM, David Booth wrote: >>>>> I've been thinking further about this, and I have another >>>>> more >> radical suggestion. >>>>> >>>>> It seems to me that including even an informative definition >>>>> of >> "generalized RDF" in the RDF spec substantially increases the risk >> that someone may mistakenly believe that "generalized RDF" is some >> form of standard RDF, when it is not. It is an extension of RDF >> that does not conform to the RDF standard. Hence it is all the more >> important to visibly warn readers about the use of generalized >> RDF. >>>>> >>>>> Actually, the more I think about it the more I am convinced >>>>> that >> the inclusion of the definition of "generalized RDF" in the RDF >> spec **at all** is a big mistake, because it substantially >> increases the risk that someone may mistakenly believe that >> "generalized RDF" is some form of standard RDF, when it is not. >>>>> >>>>> Thus, my second suggestion is to entirely remove the >>>>> definitions of >> generalized RDF triple, graph and dataset from the RDF Concepts >> document >>>>> >> https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#section-generalized-rdf >> >>>>> >>>>> >> If the RDF Semantics document needs to define the notion of >> generalized RDF to simplify the semantic rules, then I guess a >> definition could be included in that document, *with* a big fat >> warning saying that this definition is included only to simplify >> the specification of the formal semantics, and does not constitute >> a part of the RDF standard. >>>>> >>>>> David >>>>> >>>>> >>>>> On 08/01/2013 11:20 AM, David Wood wrote: >>>>>> Hi David, >>>>>> >>>>>> I acknowledge your comment and your concern. I >>>>>> *personally* agree >> with >>>>>> you that we need to carefully word this section of RDF >>>>>> Concepts. >>>>>> >>>>>> The next RDF WG meeting that I will be able to attend is >>>>>> 21 >> August, >>>>>> so I will put this on the agenda for that meeting. >>>>>> >>>>>> Regards, Dave -- http://about.me/david_wood >>>>>> >>>>>> >>>>>> >>>>>> On Aug 1, 2013, at 10:28, David Booth <david@dbooth.org> >>>>>> wrote: >>>>>> >>>>>>> Section 7 defines the notion of "generalized RDF", >>>>>>> triples and >> datasets, but does not adequately warn that "generalized RDF" is >> non-standard. Case in point: this has already led to some >> discussion in the JSON-LD group about whether "generalized RDF" is >> a form of standard RDF. >>>>>>> >>>>>>> I suggest rewording section 7 to the following, using a >>>>>>> "NOTE" >> call-out: >>>>>>> [[ <p>It is sometimes convenient to loosen the >>>>>>> requirements on <a>RDF triple</a>s. For example, the >>>>>>> completeness of the RDFS entailment rules is easier to >>>>>>> show with a generalization of RDF triples. </p> >>>>>>> >>>>>>> <p>A <dfn>generalized RDF triple</dfn> is an RDF triple >>>>>>> generalized so that subjects, predicates, and objects are >>>>>>> all allowed to be IRIs, blank nodes, or literals. A >>>>>>> <dfn>generalized RDF graph</dfn> is an RDF graph of >>>>>>> generalized RDF triples, i.e., a set of generalized RDF >>>>>>> triples. A <dfn>generalized RDF dataset</dfn> is an RDF >>>>>>> dataset of generalized RDF graphs where graph labels can >>>>>>> be IRIs, blank nodes, or literals.</p> >>>>>>> >>>>>>> <p class="note" id="note-generalized-rdf"> Any users of >>>>>>> generalized RDF triples, graphs or datasets need to be >>>>>>> aware that these notions are non-standard extensions of >>>>>>> RDF and their use may cause interoperability problems. >>>>>>> There is no requirement on the part of any RDF tool to >>>>>>> accept, process, or produce anything beyond standard RDF >>>>>>> triples, graphs, and datasets. </p> ]] >>>>>>> >>>>>>> Thanks, David >>>>>>> >>>>>> >>>>> >>>>> >>>> >>>> >>> >> >> ------------------------------------------------------------ IHMC >> (850)434 8903 or (650)494 3973 >> >> 40 South Alcaniz St. (850)202 4416 office Pensacola >> (850)202 4440 fax FL 32502 (850)291 >> 0667 mobile phayesAT-SIGNihmc.us >> http://www.ihmc.us/users/phayes >
Received on Sunday, 4 August 2013 21:08:27 UTC