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Re: Are generic resources intentional?

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 10 Jun 2009 09:55:21 -0500
Cc: "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>, David Booth <david@dbooth.org>, Alan Ruttenberg <alanruttenberg@gmail.com>, "noah_mendelsohn@us.ibm.com" <noah_mendelsohn@us.ibm.com>, AWWSW TF <public-awwsw@w3.org>
Message-Id: <D374299E-CD40-4325-B35F-8D8B39628DE2@ihmc.us>
To: Jonathan Rees <jar@creativecommons.org>

On Jun 10, 2009, at 9:01 AM, Jonathan Rees wrote:

> On Wed, Jun 10, 2009 at 9:28 AM, Pat Hayes<phayes@ihmc.us> wrote:
>> . Resources have to be able to Do some
>> Webbish things, participate in the Web architectural dance in some  
>> way. They
>> are agents, not files.
>
> Hmm, I haven't come across this.  If you could give some a reference
> that would help.

Sorry, I'm making this up as I go along.

>
> In the ICSE 2000 paper Roy says:
>
> "The key abstraction of information in REST is a resource. Any
> information that can be named can be a resource: a document or image,
> a temporal service (e.g. "today's weather in Los Angeles"), a
> collection of other resources, a moniker for a non-virtual object
> (e.g. a person), and so on."
>
> Are images agents?

No, but I think the key phrase in the above is "which can be named",  
which seems to be playing the same role that "has an identity" was  
once used for. This notion of "named" or "identified" doesn't mean  
'referred to': it means, in this context, "can be accessed by using  
its name", which when you unpack it carefully means something like "is  
being handled by some active system or agent which can deal  
effectively with transfer protocols for appropriately syntaxed names".

But OK, I concede that this quote does muddy my water. I am puzzled.  
Roy also says that a resource is conceptually a function from times to  
representations (and in 2000, that a solid, physical book on a shelf  
is also a resource, a position which *really* does not make sense.)  
So, you tell me, is an image a function from times to representations  
(of it, the image)? Or does that better describe an image inside  
something that is functionally capable of emitting representations?  
Whatever those are, and whatever it is to emit, that surely requires  
some kind of activity, not being purely passive. Images don't do  
anything. Same for files.

> What happens inside a server is a possibly complex series of handoffs
> and script invocations. At some point there may (or may not) be some
> entity that is specific to the request-URI as opposed to being generic
> across several of them. That entity may then be either passive (e.g. a
> web page, file, or database) or agent-like (e.g. an ongoing
> computational process, a robot or other off-the-web service). But this
> would all be implementation detail...   from the outside there would
> be no way to tell whether the resource were passive, with the server
> acting as agent, or itself an agent, with the server being a passive
> intermediary.

But you do know that SOMETHING is active, or you wouldn't have got a  
response. Maybe you don't know exactly what, and maybe you don't care.  
But you can infer that some active thing *exists*, and you can tell  
yourself that the URI denotes *that* (whatever it is).

> (If I do a POST and the robot arm moves, did the
> resource move it, or did the server?)

I'd say in that case that the arm could be the resource, conceptually.  
Of course, the arm there includes a great deal of electronics and  
software, but then robot arms do.

It is always OK to choose some 'larger' system to be the resource,  
note. But I don't think it makes sense to say that every little  
passive digital piece of chump-change is an information resource. LIke  
I say, if that were the case, the Web would have already been there  
before the internet was invented.

> So I'm not sure what the
> consequences of a choice would be, in the situation where there is a
> choice (e.g. where Apache serves up a file).
>
> Certainly this is a big difference in the way you and Tim talk about
> the web, whether consequential or not.

Hmm, seems to me I learned it from Tim, but maybe my exposure has been  
limited.

Pat


> Given the amount of active
> content out there I think I would prefer to say that passive web
> resources are just a special kind of agent, as you say, rather than
> attempt to shoehorn active content into the generic-resource model.
>
> Jonathan
>
>
>

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Received on Wednesday, 10 June 2009 14:56:36 GMT

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