- From: Pat Hayes <phayes@ihmc.us>
- Date: Mon, 14 May 2012 00:11:18 -0500
- To: Richard Cyganiak <richard@cyganiak.de>
- Cc: Peter F. Patel-Schneider <pfpschneider@gmail.com>, David Wood <david@3roundstones.com>, public-rdf-wg WG <public-rdf-wg@w3.org>
On May 13, 2012, at 3:48 PM, Richard Cyganiak wrote: > Hi Pat, > > On 13 May 2012, at 07:59, Pat Hayes wrote: >> A modified suggestion: put the rules into the same document as the test cases. > > As said before, the test cases document is to document a collection of stuff that can be automatically checked using a test harness. Hmm, OK. Then let us have a wholly new document which just describes the rules, or perhaps in an appendix to the Primer. I would like to separate the rules from the semantics: they really are separate topics. The rules are a kind of introduction to implementing reasoners, although they are pretty awful when viewed in this light. > >> We will try to make this as complete as we can, but will not claim nor set out to prove that they are indeed complete. (That alone will get rid of pages of impenetrable maths.) > > Well, we have a form that many readers reportedly find easier to understand, and one that they find harder. As long as they're known to be equivalent, They are not equivalent. The rules specify one, rather bad, way to implement a reasoner, and do so in an ad-hoc manner invented for this document. The model theory gives a general method for determining validity of any set of inference rules and a general definition of consistency, using ideas which have been accepted as foundational for half a century. To make the first one normative is simply ridiculous. > I think it doesn't matter too much which one is informative and which one is normative. I think it matters hugely. > If, on the other hand, we do not know whether both are equivalent, then the only responsible thing is to make the easier form normative. > >> Along with this, let us strip out all the attempted exposition and 'tutorial' content from the semantics document and have it be strictly for readers who know what words like "interpretation" and "consistent" mean. This will be enough for readers who need to know this stuff, and apparently this tutorial content is irrelevant for the general reader in any case, since none of them can understand it. It will make the document a lot shorter. > > I'm ok with that. It's a specification, not a primer. Glad we agree :-) > >> I couild try to write a short explanation of how to test a proposed inference for validity by constructing a formal counterexample. This might give naive readers a better grasp of how to connect interpretations with rules, in fact. It could also go into the 'test cases' document, or even into the primer somewhere (?) > > Not keen on having this in the test cases. Covering more of the semantics in the Primer is an intriguing idea. It might help. It can be expressed in non-mathematical terms. I will take a stab at producing some text for this. Pat > >>>> I think that it might be a good idea to put a warning at the beginning of the document telling people that this is a formal description of the semantics of RDF and that readers should be first familiar with several of the other RDF documents. >> >> Or that it is intended for readers familiar with the basic ideas of formal semantics, yes. > > Yes, that too. > > Best, > Richard > > > >> >>> >>> +1 >>> >>> Richard >>> >>> >>> >>>> >>>> peter >>>> >>>> >>>> On 05/04/2012 07:53 AM, Richard Cyganiak wrote: >>>>> Hi Peter, >>>>> >>>>> On 4 May 2012, at 09:52, Peter F. Patel-Schneider wrote: >>>>>> Well I think that it would be a horrible idea to deemphasize the semantics. >>>>>> >>>>>> I'm also completely unsure as to what name could be any better than RDF Semantics. >>>>> Let's consider who reads the RDF Semantics document, and for what reasons. From what I gather, we can identify a number of different cases. I'm sure there are many more: >>>>> >>>>> 1) Spec writers read it, in order to understand how to make their specifications compatible with other specifications in the RDF stack. For example, neither the RDB2RDF WG nor the SPARQL WG could have done its work without knowing the things formally specified in RDF Semantics. >>>>> >>>>> 2) Implementers of various specs (incl. RDF, RDF Schema, SPARQL) read it, in order to understand how their systems should behave, especially with regard to datatypes and RDFS inference. >>>>> >>>>> 3) Authors of RDF Schema vocabularies read it, in order to understand the consequences of declaring domains, ranges, subproperties and so on. >>>>> >>>>> 4) RDF newbies read it, because this is where they happened to end up after some googling or link-clicking and they don't understand the big scheme of things yet. >>>>> >>>>> How well does the current document serve these needs? >>>>> >>>>> For 1), I think it works well. >>>>> >>>>> For 2) and 3), I think the document as it stands does not serve these readers well, and it could do a *much* better job. We have reports that such readers tend to find the informative entailment rules in Section 7 extremely useful, and much of the rest of the document rather impenetrable. It has thus been suggested that the entailment rules should be given more prominence. One minimally invasive way of achieving this would be to just move the words “normative” and “informative” around a bit. I suppose this is what Ivan refers to when he says “reorganize to make the rules normative and deemphasize the model-theoretic semantics”. >>>>> >>>>> For 4), the document as it stands doesn't work at all, and it can't, because that's not its purpose. In fact, when newbies try reading this document, it's pretty much guaranteed to end in disaster. I think we all agree that this is *not* the document you should be looking at in your first encounter with RDF. There isn't *too* much we can do about this, but I think that a title that is a bit scarier to newbies could help. Can we put something like “model theory” or “formal representation logic” into the title? >>>>> >>>>>> Of course, if the WG wants to make RDF no longer be a formal representational logic, then .... >>>>> I thought RDF is a data model? >>>>> >>>>> Best, >>>>> Richard >>>>> >>>>> >>>>> >>>>>> peter >>>>>> >>>>>> >>>>>> On 04/25/2012 11:27 AM, David Wood wrote: >>>>>>> Hi Peter and Pat, >>>>>>> >>>>>>> The RDF WG briefly discussed the need for an RDF Semantics editors draft at today's telecon. I am aware that there are a lot of open issues and therefore hard to produce a draft, but perhaps it makes sense to have a single document that lists the issues in one place. >>>>>>> >>>>>>> In any event, we would like to discuss this at next week's telecon if you can make it. Thanks. >>>>>>> >>>>>>> Relevant comments from IRC (no log published yet since the meeting isn't over): >>>>>>> [[ >>>>>>> ivan: one thing that came up early was discussion to change title of RDF Semantics document, reorganize to make the rules normative and deemphasize the model-theoretic semantics AlexHall @ 11:20 >>>>>>> ... think it's a good thing to do but huge amount of editorial work AlexHall @ 11:20 >>>>>>> cygri: is there an editors draft of RDF Semantics yet? 11:21 >>>>>>> [no] 11:21 >>>>>>> cygri: given that there are larger changes to the doc, would feel better if there were an editors draft by now. 11:21 >>>>>>> guus: suggest we should put it on the agenda for next week >>>>>>> ]] >>>>>>> >>>>>>> Regards, >>>>>>> Dave >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>> >>> >>> >>> >> >> ------------------------------------------------------------ >> 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 >> >> >> >> >> >> > > > ------------------------------------------------------------ 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 Monday, 14 May 2012 05:11:54 UTC