Saturday, April 30, 2005

Harry Halpin on httpRange-14 

httpRange-14 notes:: "What do URIs identify?
In essence, one reason Web works because using a web protocol like http(Hypertext Transfer Protocol), one can from a client send a request to a server to do an operation such as HTTP GET for a given URI and dereference something, often a web-page. However, this very basic feature of the Web is bedeviled by a question: 'What is the range of the HTTP dereference function?' In other words, what do URIs identify? In theory this question has been solved by the W3C TAG's AWWW: URIs refer to anything. Upon inspection, the official definition is actually circular: 'We do not limit the scope of what might be a resource...it is used in a general sense for whatever might be identified by a URI.' The question then arises that if a resource is just anything that could theoretically be with a identified URI, is there anything that can not be identified? It would seem not. This view is given by the AWWW as 'our use of the term resource is intentionally more broad. Other things, such as cars and dogs ... are resources too.' However, referring to a web-page and the car in my garage are similar acts, but they are not exactly the same. The essential difference is this: in the first case on the Web we have physical, connected, access to the Web-page, while in the second case if we are using the Semantic Web to refer to my car, we only the ability to refer to my car by a URI name, and this has no direct, connected, or physical access. When one uses a URI as a name there is a disconnect, as the thing named may not be on the Web.
The division between representation and resource existed but was not explicitly stated, and definitely not noticed by, most of the users of the original hypertext Web. URLs seem to be originally meant to identify the location of representations, such as HTML web-pages"

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