- From: Pat Hayes <phayes@ihmc.us>
- Date: Thu, 23 Aug 2012 00:55:18 -0500
- To: Richard Cyganiak <richard@cyganiak.de>
- Cc: Antoine Zimmermann <antoine.zimmermann@emse.fr>, RDF Working Group WG <public-rdf-wg@w3.org>, Simon Reinhardt <simon.reinhardt@koeln.de>
On Aug 22, 2012, at 4:58 PM, Richard Cyganiak wrote: > On 13 Aug 2012, at 18:29, Antoine Zimmermann wrote: >>> Note that the new Introduction section in the RDF Concepts ED >>> contains an *informative* sentence that introduces the term >>> “property” [4], and it is in line with RDF Semantics: >>> >>> [[ The predicate itself is an IRI and denotes a binary relation, also >>> known as a property. ]] >> >> This is not what the RDF semantics says. A predicate denotes a resource that must be in IP, the set of properties in the interpretation. Resources in IP are associated with a binary relation via the extension function IEXT. >> This is an important distinction since this is what allows RDF to talk about properties, classes, etc as instances. > > Ah, right. I forgot about the class/property extension stuff in RDF Semantics. > >> If predicates were denoting binary relations, the following would be RDFS-inconsistent, when it is, in fact, RDFS-consistent: >> >> :p rdf:type xsd:string . >> :s :p :o . > > Do I get this right? This would be inconsistent because the first triple says its a Unicode string, and the second triple entails that it is a property, and hence (if my phrasing above were indeed correct) a binary relation. And a Unicode string is not a binary relation. > > And in reality, as RDF Semantics defines things, the second triple only entails that the Unicode string *has a property extension*, and the property extension is a binary relation. Hence, no contradiction. Anything can have a property extension. > > Right? Right. In RDF, in fact, everything *does* have a property extension (whether you are using it or not, it is there to be used.) In this it follows ISO Common Logic, by the way. > >> This is a proposal to replace the wording in section 1.2 [1]: >> >> "The predicate itself is an IRI and denotes a property, that is, a resource that defines a binary relation." > > As usual, given that this is informative introduction text, there is a balance to be found between accuracy and simplicity. So I'd like to toss this around a bit. > > Is it accurate to say that the resource "defines" a binary relation? In what sense does it do that? Good point. > > Wouldn't it be slightly more accurate (but perhaps less understandable) to say that the predicate IRI denotes "a property, that is, a resource that can be interpreted as a binary relation"? Yes. Or more accurately still, "...which is being interpreted as a...." . > > How about the fuzzy but perhaps simpler: "The predicate IRI denotes a property, that is, a resource that can be thought of as a binary relation." Better, I agree. > > Or: "The predicate IRI denotes a property, that is, a resource that can be formalized as a binary relation." Nah, that suggest a misleading direction to push intuitions. I like the previous idea. > > I note that the overall purpose of the sentence is just to introduce the term "property" and give readers a decent intuition of what the term means. From that point of view, I still quite like the current phrasing ("The predicate IRI denotes a binary relation, also known as a property.") even though I know it's technically inaccurate. May I claim "harmless abuse of terminology" here? I think you can, yes. After all, people *can* read the actual semantics if they want to get the details absolutely right. :-) Pat > > Best, > Richard > > >> [1] 1.2 Resources and Statements. http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#resources-and-statements > > ------------------------------------------------------------ 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 Thursday, 23 August 2012 05:55:53 UTC