- From: Pat Hayes <phayes@ihmc.us>
- Date: Tue, 23 Oct 2007 18:42:27 -0500
- To: wangxiao@musc.edu
- Cc: noah_mendelsohn@us.ibm.com, Alan Ruttenberg <alanruttenberg@gmail.com>, Mikael Nilsson <mikael@nilsson.name>, Richard Cyganiak <richard@cyganiak.de>, W3C-TAG Group WG <www-tag@w3.org>
>Pat Hayes wrote: >>>noah_mendelsohn@us.ibm.com wrote: >>>>Xiaoshu Wang writes: >>>> >>>>>- The URI identifies the city. >>>>> >>>>>- The *representation* that people gets back by dereferencing >>>>>the URI with HTTP protocol is your *impression*. >>>> >>>>I don't think the word impression is really appropriate here. >>>>Let's say that I assign resource >>>>http://example.org/nonRhymingPoem to the poem that is popular >>>>with American school children: >>>> >>>> Roses are red, >>>> Violets are blue, >>>> Some poems rhyme, >>>> Some don't. >>>> >>>>If you do an HTTP GET to that URI I send you back an HTML page. >>>>The text of the poem is more or less centered. It's set out in >>>>some font of my choosing, in 25 point italic. The background is >>>>purple. I don't think the most appropriate way to describe that >>>>in English is to say that it's my impression of the poem. It's >>>>the way I choose to render the poem for your perusal. In fact, >>>>it's quite appropriate to say that the HTML page is the way that >>>>I choose to represent the program. >>>>Furthermore, I don't think we need to insist that this particular >>>>URI is only for the poem rendered in those fonts, unless that's >>>>what I say the URI is for. If I say that it's for the poem, and >>>>in a year or so someone comes up with a font I like better, I see >>>>no problem with my changing the page to use that. The URI still >>>>identifies the poem, since I say it does (presuming I've >>>>registered example.com). The HTML pages are still >>>>representations of the poem, they are not my impressions of it. >>>> >>>Yes, I agree with all that. I am perfectly clear about that. >>> >>>The problem is that at least someone does not think that >>>http://www.ihmc.us/users/phayes/PatHayes can be used to refer Pat >>>Hayes? They will say httpRange-14 dictates that >>>"http://example.org/nonRhymingPoem" can emit 200 but >>>http://www.ihmc.us/users/phayes/PatHayes must emit 303? >> >>Yes. That page violates httpRange-14 (deliberately, I might add :-) >> >>>I cannot see there is anything, at least anything objective, to >>>judge that position. The reason people think that Pat's URI is >>>wrong because when they dereference the URI with HTTP they gets >>>back an HTML page. They say, nah, Pat cannot be an HTML page, so >>>that URI is wrong. But the truth is: it is not that Pat becomes a >>>HTML page, it is a representation of Pat becomes page. What I want >>>to say in the past few days is let's clarify the difference >>>between *a resource* identified by a URI and *a representation* of >>>that resource once dereferenced via the HTTP protocol. You can >>>know something about the resource from its representation but how >>>much depends on the content of the representation and your ability >>>to handle the representation. >>> >>>If we understand URI dereference from this point of view, there is >>>no ground for httpRange-14 anymore. And there is no point to >>>distinguish what is information resource and what is not. >> >>There is a real issue, however. You or I can read what that page >>says and understand it. But programs can't. The Semantic Web needs >>a way for a program to reliably infer whether the URI denotes me or >>some HTML. If there were some universally agreed way to do this >>(say, a world-standard, universally accepted, OWL person ontology) >>then the page could use this. But there is no such way for it to >>say this in a machine-readable fashion, and so we are left with an >>ambiguity. >If the RDF representation of "http://www.ihmc.us/users/phayes/PatHayes" says: ><http://www.ihmc.us/users/phayes/PatHayes> a foaf:Person. Why a >program would confuse that? How? >>One view on this, which I have espoused elsewhere, is to simply >>accept that URI denotations are ambiguous and learn to live with >>it, by using the context to disambiguate the meaning. >If we cleanly separate the meaning of URI from its *dereference* >protocol, how can the identity of URI ambiguous? Because people often DO use the URI to denote the page/'information resource' that it dereferences. And that's not *illegal*; and in fact it is very common. So now, here I am, a dumb-as-dirt SemWeb program, and I have this URI. Does it denote what it dereferences? Or something else? How can I tell? >HTTP is just a communication protocol, established for agents to >communicate. It does not establish a context for the meaning. If >we do, we put this as a poker game, where we try to infer someone's >hand from its behavior. Is this what the web wants? No, which is why I think reading httpRange-14 as a way of 'signalling' denotation is wrong. It just acknowledges the common, widely used, natural convention that a URI denotes whatever it dereferences to, but it also allows a minimal way to side-step this in some cases, if you want it (the URI) to denote something else. Can you see any other way to do this? Pat > >Regards, > >Xiaoshu -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 cell phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
Received on Tuesday, 23 October 2007 23:42:40 UTC