- From: Patrick Stickler <patrick.stickler@nokia.com>
- Date: Thu, 02 Oct 2003 15:39:41 +0300
- To: ext John Cowan <cowan@mercury.ccil.org>
- Cc: ext Garret Wilson <garret@globalmentor.com>, "ext Hammond, Tony (ELSLON)" <T.Hammond@elsevier.com>, <www-rdf-interest@w3.org>, <uri@w3.org>
On 2003-10-02 14:44, "ext John Cowan" <cowan@mercury.ccil.org> wrote: > Patrick Stickler scripsit: > >> It is an understandable common misconception that what an HTTP >> server actually returns is what is denoted by the URI. The fact >> is that we can never be absolutely sure what resource a URI >> denotes based on what is returned by a server. In some cases >> it's easier to guess than other cases, but typically you can't >> ever be sure. Hence the car/document problem. > > This characterization of the problem is far > too mild. Consider the resource whose URI is > http://www.tagyerit.com/images/adopted/shakespeare.jpg . > You can't do a direct GET on this any more, but it's > still available (for now) in the Google cache at > http://images.google.com/images?q=tbn:IbW4adfRGVkC:www.tagyerit.com/images/ado > pted/shakespeare.jpg > > If you retrieve this resource, you will get a sequence of bits labeled > image/jpeg. But what is the resource? Is it Shakespeare? Is it a > (generic) picture of Shakespeare? Is it this *particular* image of > Shakespeare? Or is it something else altogether? Nobody can say, > probably not even the person who posted the picture to the Web. Insofar as a cache reflects what was/could be retrievable from a particular web authority, I don't see that the above case needs any special interpretation. One could fairly presume an implicit equivalence relation between the denotation of cache URIs and the original URI. I.e. <http://images.google.com/images?q=tbn:IbW4adfRGVkC:www.tagyerit.com/images/ adopted/shakespeare.jpg> owl:sameIndividualAs <http://www.tagyerit.com/images/adopted/shakespeare.jpg> . But the ambiguity of what resource is actually denoted by either URI (regardless of the nature of the representation itself) remains. >> And hence the reason for URIQA. To be able to obtain an authoritative >> answer to the questions "What does this URI denote, and what is >> that thing like?". A representation of the resource might be able >> to give a human some clues, but being able to obtain a formal, >> precise description of the resource is much better. > > A fine thing indeed. How would you formally characterize the relationship > of the above URI to Shakespeare? Well, if the above URI actually does denote Shakespeare (rather than a portrait of Shakespeare, etc.) then it really is a matter of vocabulary. If a more commonly used URI denoting Shakespeare exists, you could make an owl:sameIndividualAs assertion, but in the end, a URI is a URI is a URI and its actual denotation is meta-knowledge that is (at least presently) defined by social means, not formal. Still, if the server www.tagyerit.com was URIQA enlightened, then one could hope for a description of the resource denoted by the URI in question, stating that it denotes a historical person, who's name is William Shakespeare, who was a poet/playwright, was born on a given date, in a given place, died on a give date, etc. etc. with statements relating the person to his works, yada yada yada. Perhaps a google cache (in the future) would also contain the formal concise bounded description of the resource denoted by the URI, in addition to one or more representations that are/were accessible via that URI. Patrick
Received on Thursday, 2 October 2003 08:40:42 UTC