- From: Jonathan Rees <jar@creativecommons.org>
- Date: Thu, 12 Mar 2009 09:02:24 -0400
- To: Larry Masinter <masinter@adobe.com>
- Cc: "www-archive@w3.org" <www-archive@w3.org>
On Wed, Mar 11, 2009 at 7:17 PM, Larry Masinter <masinter@adobe.com> wrote: > I think the right venue for resolving some of the philosophical questions of > identity and URIs belongs in the IJCAI conference workshop and not on the > TAG agenda. No question. (I don't know whether I can attend, but will look into it.) > Many TAG and other semantic web discussions about identity and reference ask > questions about equality, identity, counting, and distinguishing > “resources”, for example, “ Is the resource identified by URI X the same as > the resource identified by URI Y?” > > “How many resources does a URI identify?” The question is important in any context where one might consider the correctness of substituting one URI for another. Such situations do not necessarily fall under the TAG agenda. Actually I don't recall these issues ever having come up on TAG time. The TAG is not really very interested in this level of analysis. > My perspective is that these questions are not well formed. Equality and > countability are mathematical operations. The space of “resources” is not a > set, has no well-defined notion of “identity”, and there is no way, in > general, of determining “equality”. I would not say "mathematical" unless you consider any consideration of equivalence of syntactic things to be mathematical. But clearly substitutability is a function of interpretation (semantics), and that is probably what you mean by both "mathematical" and "context". > Since you cannot, in general, determine equality of two resources identified > by two different URIs, counting them or arguing “sameness” doesn’t work. Agreed that without agreeing first on semantics, the question is meaningless. But that is true of all questions. Just because you don't know enough about some things to distinguish them doesn't mean you shouldn't try to hone your theory so as to resolve the question - either by fiat, by desired ensuing behavior, or by recognizing that the answer is inherently unknowable (your theory, or state of knowledge, is incomplete). I don't see these questions as being particularly philosophical. With RDF and its derivatives you are interested in the very practical problem of automated inference (broadly construed to include search). In order for inference to be meaningful, you have to choose an inference system and suitable axioms, sometimes called a logical model. When you interpret the URIs in some particular way you get a "model" in the opposite sense (that of model theory, where the problem-domain interpretation is a model of the theory, not vice versa). When inference gives you correct results under an interpretation that is helpful to you, you can declare the whole programme a success for you. I think this is all pretty clear, and spelled out in Pat's RDF semantics document, although perhaps not widely understood. So I consider these to be much more engineering questions than philosophical ones. The thing I would like to contribute is a document (finding?) that relates HTTP to RDF and puts the httpRange-14 issue to rest so we can stop bickering about it. I would like to say that there are many possible theories that might relate the two protocols (stretching a bit here by calling RDF a "protocol" but I do so to make a point). People who need such theories (e.g. for the purpose of expressing metadata) might choose to agree on one or two of them among themselves so that they can integrate data. Unfortunately we have at least three such logical models right now that are mutually inconsistent, and perhaps all are needed. I say: So it goes, that's the nature of the beast. Different models for different purposes. As long as you don't simultaneously apply inconsistent models to the same URI, everything should work out OK. The httpRange-14 rule can be reinterpreted: If you make an RDF theory of HTTP or of some 200-yielding HTTP resource, please try to put the RDF referent of the URI in classes that are fairly closely tied to the way HTTP is used - e.g. documents, web pages, REST resources, web services, and so on. Make "identification" under HTTP as close as you can to "identification" in a model of your RDF theory. This is just what some set of people consider good RDF practice (for reasons I needn't go into again). "Information resource" does not have ontological status as a "class", nor does it have any kind of normative status as establishing a normative HTTP/RDF translation is not desirable. IR is just a shorthand for certain considerations around relating the two protocols, improving the chances of consistency when independent logical models using the same URI collide. If we could relate HTTP to RDF, this could set an example for relating other protocol pairs, and if the approach became methodical, we might be able to make suggestions about some general theory of the (recommended) meanings of URIs - identifying equivalences, types, and relations in one domain and showing how they correspond to equivalences, types, and relations in another. Personally I think HTTP/RDF is the only case worth pursuing, and it should be useful to limit the hunt to this one quarry. Whether anyone else will like this, I'm not sure - certainly the semantic web view is different from the above, since it thinks the world is just one big happy ontology. I don't buy that. (RDF != semantic web) Feel free to join AWWSW, which is where we talk about this kind of thing (although I've put a temporary gag order on discussion of what is an IR).
Received on Thursday, 12 March 2009 13:03:08 UTC