- 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
+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 UTC