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   Is Resource/Representation a fruitful abstraction? (was Re: [xml-dev]man

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On Sat, 25 Jan 2003 22:13:27 +0000, Miles Sabin <miles@milessabin.com> 

> As far as network protocols and software are concerned, abstract 
> Resources do no work at all. What matters in a retrieval context is that 
> there be a functioning server that's capable of returning a response, 
> maybe with a response entity, maybe without.
> So, if there were no Resources, or more than one, or different ones on 
> different occasions, what would break? Can you name one piece of working 
> software that'd stop working if Resources were to vanish in a puff of 
> existential smoke overnight?

Weeeellllll, I guess it depends on what a "Resource" is.  I think we're all 
comfortable with the assumption that http://www.cnn.com is a "resource" for 
up to date news.  Whether that is a Resource in the RESTifarian sense is 
another matter.  Certainly it returns a different representation every few 
minutes (and for all I know it may support content negotiation and return 
raw text or WML or whatever on demand).  If the idea of cnn.com as a 
Resource totally vanished and one had to retrieve the news with a URL that 
qualified the time, e.g. http://www.cnn.com/2003/January/24/19.47 then a 
whole lot of people would stop using the site, I suspect.

Still, I think there's a lot of existential latitude between "cnn.com is a 
resource for news" and "http://www.cnn.com is a Resource representing the 
news and one retrieves a Representation of the up to the minute news by 
dereferencing it, and one can make assertions about 'news' by using 
http://www.cnn.com as an identifier of that abstract concept."  I can't say 
that the second is wrong, but I will assert that the empirical success of 
CNN.com as a website says absolutely nothing about its theoretical validity 
or utility. Are the webmasters at CNN.com adhering to the URI/REST religion 
by updating the site with a new representation every few minutes?  I don't 
think so -- they're updating the content.  Empirically, websites (a concept 
never discussed formally in these discussions, AFAIK) do what their 
maintainers configure them to do: some can return RDF descriptions of the 
abstraction their owner hopes to identify, some return static HTML 
irrespective of the HTTP content type headers, some of which try very hard 
to implement RFC 2396 ... but most just sortof do whatever the webmasters 
feel motivated to do with them.  "Resource" and "Representation" seem like 
reasonable abstractions for all this, but they are VERY abstract 

Nevertheless, while I would quibble with some of the more categorical 
statements that this doesn't work at all, I have to agree with the gist of 
what Miles, Simon, and others seem to be saying -- the TAG is trying to 
squeeze WAY to much juice from this rather dry fruit. If they are trying to 
understand the actual principles of the Web by focusing on URIs, resources, 
and representations, I'm extremely skeptical that they will produce 
anything particularly useful to guide Webmasters, Semantic Web researchers, 
Web services theorists or practicioners, etc.

[speaking only for myself, wearing no W3C or Day Job  hat]


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