- From: David Booth <david@dbooth.org>
- Date: Tue, 29 Oct 2013 09:54:34 -0400
- To: Pat Hayes <phayes@ihmc.us>
- CC: public-rdf-comments <public-rdf-comments@w3.org>
Hi Pat, On 10/29/2013 12:53 AM, Pat Hayes wrote: > > On Oct 28, 2013, at 8:55 PM, David Booth <david@dbooth.org> wrote: > >> Hi Pat, >> >> I'm trying to understand the rationale for defining the notion of >> "identifies" as being distinct from "denotes". > > The RDF semantics *defines* the notion of denotation. It *uses* the > notion of identification, which is also used and described in a > number of other W3C standards and publications. The RDF semantics > document does not set out to define this notion: it simply refers to > it as being any any widely accepted notion of how IRIs map to > meanings which is used and accepted externally to RDF. Thus, for > example, the IRI http://www.w3.org/2001/XMLSchema#int *identifies* > the datatype called 'int' defined in section 3.4.17 of the W3C XML > Schema Definition Language (XSD) 1.1 Part 2 Recommendation published > on 5 April 2012, http://www.w3.org/TR/xmlschema11-2/#int. That this > is true is not determined by anything in the RDF semantics: it is > simply a fact, established by a complex set of social, linguistic and > technical conventions about how certain IRIs are attached to accepted > meanings. In order to ensure that RDF denotation agrees with this, so > that interpretations (in appropriate cases) map > 'http://www.w3.org/2001/XMLSchema#int' to that datatype, it is > necessary to stipulate that denotation as defined in RDF coincides > with this socially defined mapping from IRIs to meanings; and that, > in turn, requires that we have a way to refer to this (and similar) > mappings. That is why we use the term "identify" in the RDF Semantics > document to refer to this (indeed to any defined-externally-to-RDF) > mapping. (We could just say something like, these IRIs denote what > everyone would expect them to denote, but that would probably not be > considered to be acceptably precise.) I think I see what you're getting at, but as written it sounds as though there are two separate notions being used within the formal semantics, whereas I think what you mean is that one of these terms ("identify") is intended to refer to the vague notion of identify/denote that is used *outside* of the formalization, and the other ("denote") is intended to refer to the precise *formalization* of that notion in the RDF semantics. Is that correct? BACKGROUND: We have pre-existing terms "identify" and "denote", and associated with these pre-existing terms we have pre-existing notions of what they mean. In both cases those pre-existing notions generally refer to some kind of mapping from names to meanings. THEREFORE: If I'm understanding properly, "identify" is being used in the RDF Semantics document to refer to this vague pre-existing notion of a mapping from names to meanings, whereas "denote" is being used to refer precisely to the *formalization* of that notion as a mapping in a particular interpretation. Is that correct? If so, then that would alleviate my concern about having two different IRI mappings defined, but I think the description of "identify" in section 4 should be clarified, because at present it sounds like "denote" is refering to an *alternate* notion of a mapping from names to meanings, rather than a formalization of the *same* notion. I would suggest changing the second paragraph of section 4 to something like: [[ Informally, IRI meanings may be determined in a number of socially defined ways external to the RDF semantics. When we wish to refer to this informal, socially defined mapping from IRIs to meanings, we will use the word *identify* and its cognates. In contrast, when we wish to refer to the precise formalization of this notion in the RDF semantics, we use the words *denotes* and *refers* interchangeably as synonyms for the relationship between an IRI or literal and what it refers to in a given interpretation, itself called the *referent* or *denotation*. For example, the fact that the IRI http://www.w3.org/2001/XMLSchema#decimal is widely used as the name of a datatype described in the XML Schema document [XMLSCHEMA11-2] might be described informally by saying that the IRI identifies that datatype. But in the formal semantics it may or may not refer to that datatype in a given interpretation (depending on whether it is /recognized/). As another example, an IRI used as a graph name identifying a named graph in an RDF dataset could refer, in a particular interpretation, to something different from the graph it informally identifies. ]] > >> As I mentioned before, at first reading this appeared to me to be a >> contrived distinction that was created to avoid having a URI denote >> more than one thing. > > That was not the purpose of making the distinction. Got it. (I think.) Thanks for the clarification. > >> But you argued that it was needed for the datatype semantics to >> work out, so I wanted to understand that. >> >> http://www.w3.org/TR/2013/WD-rdf11-mt-20130723/#literals-and-datatypes >> >> >> Section 7 says: "We assume that a recognized IRI identifies a unique datatype wherever it occurs, and the semantics requires that it refers to this identified datatype." Therefore, for a recognized IRI, the "identifies" mapping is the same as the "denotes" mapping. So at least for recognized IRIs, there appears to be no need to distinguish between "identifies" and "denotes". > > The necessity is to make the assertion, that in this case denotation > is (defined to be) identical to identification, not be a tautology. > As it stands, this is a definition (of denotes) which uses an > predefined term (of identifies) in its body. If these two terms were > considered to be identical in meaning, this definition would be > vacuous. But in any case, they are not identical in *meaning*. Okay, sounds good. Thanks, David > >> Is the distinction then needed for non-recognized IRIs? But I >> don't think I saw any semantic conditions or entailment rules for >> non-recognized IRIs. Are there some that I missed? I'm not seeing >> how the datatype semantics requires a distinction between >> "identifies" and "denotes". Can you explain? Please feel free to >> shift your reply to www-archive@w3.org instead of posting to this >> list. >> >> Also, a few small editorial issues/typos: >> >> 1. Two typos in this sentence: "RDF processors which are not able >> to determine which datatype is identifier by an IRI cannot >> recognize that IRI, and should treat any literals type with that >> IRI as unknown names." s/identifier/identified/ s/type/typed/ > > Yes, others had noted these. Now fixed. > >> >> 2. "Such literals SHOULD be treated like IRIs and assumed to >> denote" should be "Such literals SHOULD be treated like IRIs and >> SHOULD be assumed to denote"? > > No, because this follows from the first. But it could read " > ...SHOULD be treated like IRIs and hence assumed to denote..." > >> >> 3. "A literal with datatype d denotes the value obtained by >> applying this mapping to the character string sss: L2V(d)(sss)." >> should be "A literal composed of character string sss with datatype >> d denotes the value obtained by applying this mapping to sss: >> L2V(d)(sss)."? > > Yes, I will make that change in the next edit. > > Pat > >> >> Thanks, David >> > > ------------------------------------------------------------ IHMC > (850)434 8903 home 40 South Alcaniz St. (850)202 4416 > office Pensacola (850)202 4440 fax FL > 32502 (850)291 0667 mobile > (preferred) phayes@ihmc.us http://www.ihmc.us/users/phayes > > > > > > > > > >
Received on Tuesday, 29 October 2013 13:55:08 UTC