- From: Paul Prescod <paul@prescod.net>
- Date: Thu, 04 Jul 2002 11:09:40 -0700
- To: Patrick Stickler <patrick.stickler@nokia.com>, WWW TAG <www-tag@w3.org>
Patrick Stickler wrote: > >... > > So when a Semantic Web agent dereferences the URI denoting an RDF > Schema containing statements, what it gets back may not be that > actual schema, yet it may in fact be encoded in RDF/XML so the > agent has no way to know if the schema it recieves is the actual > and complete schema it asked for? What it got back was a representation of the schema. Presumably the provider feels that that representation is sufficiently representative of the schema. You are trusting the provider in any case, so I don't see a problem. >.... > And *here* is the crux of the issue. REST/HTTP is for human consumption, > and the fact that GET can return something other than the resource > (or as Jonathan puts it, a representation of 'full fidelity') makes > it unsuitable for the Semantic Web. You have known since the beginning of the discussion that GET could return something other than the resource or "a representation of full fidelity." Now you are shifting the goal posts. >... > Fair enough, but in practice, folks *do* use the same URI to denote > both the non-digital resource and some representation of the > resource. They cannot. By definition their URI denotes the resource (whether digital or not). > That is *exactly* what will be *recommended* by having namespace > names resolve to namespace documents! No?! Not at all. The URI does not denote the namespace document. There happens to be a well-established algorithm for certain kinds of URIs to fetch representations associated with them. That does not change what the URI denotes. If you are a programmer then you are probably aware that you can put a pointer in N hashtables and thus have N different things associated with that pointer. That doesn't change what the pointer points to. >... > RDF is fully able to reason about both resources and representations > of resources. Presuming the resources and all its representations > have different URIs that are used consistently. It would be trivial to extend RDF (or perhaps URIs) to make both resources and representations *first class*. And in fact, this is necessary because it is ALREADY THE CASE that some URIs have both an XHTML, and an XML and a Docbook representation. Therefore if you want to reason about them, you need a way of describing which representation you are reasoning about. Once you've solved this problem the solution for resources will just fall out of it. How would you use RDF to say that the "fifth element of the XML representation of 'foo' is an element of type 'bar'" and the "'seventh element of the XHTML representation of 'foo' is an element of type 'A'". If, given the appropriate primitives (element numbering, element types, etc.) RDF cannot say this because it cannot address representations or distinguish between representations and resources then RDF is not yet sufficient to work with the deployed Web architecture. Once you can distinguish between representations, it will be trivial to add a little feature for distinguishing between representations and resources. -- Come discuss XML and REST web services at: Open Source Conference: July 22-26, 2002, conferences.oreillynet.com Extreme Markup: Aug 4-9, 2002, www.extrememarkup.com/extreme/
Received on Thursday, 4 July 2002 14:10:15 UTC