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Re: Issues, trout ponds and other dangerous regions

From: Geoff Arnold <Geoff.Arnold@Sun.COM>
Date: Mon, 17 Feb 2003 18:16:02 -0500
To: Francis McCabe <fgm@fla.fujitsu.com>
Cc: www-ws-arch@w3.org
Message-id: <3E516D32.7080400@sun.com>

+1 for all three nettles.

Francis McCabe wrote:

>
> David gives an eloquent defense of REST in
> [http://www.w3.org/2002/02/mid/
> 007d01c2d325$5c30fc00$c10ba8c0@beasys.com;list=www-ws-arch]; however it
> appears that he re-opens issues that need resolving.
>
> In the current WSA document, in several places, it is stated that Web
> services are NOT tied to specific technologies and protocols (such as
> HTTP, SOAP, WSDL etc.) In fact, currently, the ONLY hard nailed-down
> technology choices are URIs and XML.
>
> If the WSA is to be technology neutral, then it is not appropriate to
> `bang on about' POST vs GET in the document; although constraints such
> as idempotency are definitely `in scope'. On the other hand, if the WSA
> is to be technology centered, then we need to make that choice
> explicit, and soon.
>
> The second nettle is more conceptual: the distinction between resources
> and services. There is a relationship, but perhaps not one that is
> immediately obvious. In my opinion these concepts are at different
> levels of abstraction: a resource is an entity that has an actual
> presence and a service is a means of achieving tasks. Services require
> realizations, and such realizations are resources; but resources can be
> `of' anything and are not tied to services. On the other hand, services
> have descriptions which are not of the service itself but of how to
> interact with them.
>
> This distinction is important because, if the focus is on services as
> opposed to resources, then a large number of concepts need to be `put
> into place' that have no relevance to the strict resource view. A good
> example is the service provider. It is an important concept for a
> service oriented architecture; but has no special equivalent for
> resource. (Owner, however, is a concept that applies to both.)
>
> Finally, there is the hoary old one concerning generic interfaces vs.
> specific interfaces. Again, so far, we have been pretty muddled about
> this. [Personal opinion: it is not possible to completely capture the
> semantics of a message without grasping both the verb and the object of
> the message. Definitely there are different styles of architecture,
> where there is a rich though generic set of verbs that everyone is
> expected to agree on, and where there is an essentially infinite set of
> verbs and everyone is expected to come up with their own definitions. I
> am somewhat persuaded of the merits of the generic case; but its a can
> o'worms defining the spanning set.]
>
Received on Monday, 17 February 2003 18:17:13 GMT

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