As I see this case, here are two types of web client: 1) a client working via 
SOAP/HTTP stack; 2) a client working via HTTP only, like a Web browser.

In the first case, it is, probably, a Web Service client (counting all 
marshaling/unmarshaling operations that regular browser does not do so far). 
So, the Web Service client has to be aware of redundant service, similar to the 
"cluster aware EJB Client stubs" implemented awhile ago in WebLogic App. 
Server. If SOAP returns the error - switch to another provider.

In the second case, if "get _nothing_  which doesn't fit into the 404 
processing" is the only 'response', the conclusion is simple - such kind of 
client is unsuitable for distributed computing and, in particular, for SOA. The 
client has to be Simple, but not Stupid Simple.

- Michael

Gregg Wonderly <[EMAIL PROTECTED]> wrote:                                  
Steve Jones wrote:
 > On 19/12/06, Mark Baker <[EMAIL PROTECTED] <mailto:distobj%40acm.org>> wrote:
 >  > But to answer your question, we make it painless by using an
 >  > architectural style, standards, and software best practices which can
 >  > accomodate change. I can't claim that any change to an app using a
 >  > Web based stack won't result in a broken application, but they're far
 >  > more robust than those built atop a Web services stack.
 > 
 > Hang on Mark, if someone turns off the server then you don't get a
 > 404, you get nothing at all. With a SOAP client you get a SOAP fault
 > from the client due to non-connection, with REST you get _nothing_
 > which doesn't fit into the 404 processing.
 
 In particular, in line with my previous posting, how in the world does the web 
 client now know what else to try to get "service"?  The hypermedia that 
 contained the "broken link", would have to provide the alternate navigation 
 choice.  There are examples of this visible on, for example, sourceforge 
 download pages.  But, the user has to "pick" the next best choice based on 
 "their knowledge" which is very disconnected from the services' knowledge of 
 their own state.  But, the client can't talk to a service that it can't 
connect 
 to.  This is a particularly troublesome part of web/REST/http design.
 
 Gregg Wonderly
 
     
                       

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