What I'm saying is that I worked on a project where we used BPEL fragments as attachments to the content messages to indicate the next stages of the process flow. The BPEL doc was fixed after the point of negotiation but was effectively a state machine anyway.
WS clients don't have to be compiled (I personally prefer it most of the time) and can be done dynamically, its only XML doc handling after all. So not theoretical, but definitely not a mainstream application. Steve 2008/9/1 Alan Dean <[EMAIL PROTECTED]>: > There is something stopping it: Compiled proxy clients. > > Also, WS-* is designed to be agnostic of HTTP so it doesn't have a > redirection mechanism built-in (that I am aware of). The reality of > the WS-* toolset is a formalisation of fixed endpoints. > > Perhaps you are correct in saying that theoretically WS-* can be > dynamic (although it seems to me that doing so would require every > service invocation to be preceded by a WSDL request - which raises > WSDL<->invocation choreographic issues of it's own as they are > separate requests) but in practice, such services do not exist. > However, in REST, hypermedia is baked-in to the architectural style as > a formalised constraint. Very different. > > Alan > > On Sun, Aug 31, 2008 at 6:31 PM, Steve Jones <[EMAIL PROTECTED]> wrote: >> There is nothing stopping a WS application returning a WSDL or even a >> BPEL fragment to indicate its next valid call. So the fixed-endpoints >> thing isn't a limiting thing of WS, it could be argued that in a goal >> oriented choreography that a more formal document exchange is liable >> to be more effective (e.g. vendor managed inventory) as it enables the >> async exchanges which implies some form of long term commitment to >> endpoints. >> >> Steve >> >> 2008/8/31 Alan Dean <[EMAIL PROTECTED]>: >> >>> Michael, >>> >>> I think that, from the perspective of REST, the statement that the >>> participants "may not change the Internet locations of the end-points >>> (w/o breaking the contract)" is incorrect. >>> >>> Whilst this may well be true of WS-*, the uniform interface constraint >>> of REST means that the application state is surfaced via hypermedia - >>> not fixed endpoints. >>> >>> Regards, >>> Alan Dean >>> >>> On Sat, Aug 30, 2008 at 7:40 PM, Michael Poulin <[EMAIL PROTECTED]> >>> wrote: >>>> I think Rob is right about "URI and HTTP verb semantics" (?) >>>> >>>> Now, if we get back to WS-CDL and its Global Contract, we end up with >>>> the >>>> contract for entire choreography with frozen set of URI/Ls. That is, the >>>> participants may not change the messages only but also may not change >>>> the >>>> Internet locations of the end-points (w/o breaking the contract) unless >>>> they >>>> start to operate with DNS aliases. Am I right? >>>> >>>> - Michael >>>> >>>> ----- Original Message ---- >>>> From: Rob Eamon <[EMAIL PROTECTED]> >>>> To: [email protected] >>>> Sent: Saturday, August 30, 2008 5:18:56 PM >>>> Subject: [service-orientated-architecture] Re: Distinction between >>>> "Choreography" and "Orchestration" >>>> >>>> I'm not a REST practitioner, but would this be covered via a >>>> combination of URI and HTTP verb semantics? URI would indicate the >>>> appropriate resource, eg. Order, Payment, etc. PUT/POST would "place >>>> order", "amend order" and "make payment" (I'm unclear on whether put >>>> or post would be appropriate here), DEL would cancel. >>>> >>>> Minimizing/eliminat ing the mixing of the verb/action into the >>>> document being exchanged would seem to be a good thing to strive for. >>>> >>>> -Rob >>>> >>>> --- In service-orientated- architecture@ yahoogroups. com, "Ashley at >>>> Metamaxim" <ashley.mcneile@ ...> wrote: >>>>> >>>>> To bring this whole thing back to the REST vs. SOAP issue: >>>>> >>>>> All the approaches to choreography that I have seen, including but >>>>> not limited to WS-CDL, require that the choreography integration >>>>> infrastructure be able to identify the messages exchanged between >>>>> the participants at the "business semantics" level: i.e., >>>>> that "Place Order", "Amend Order", "Cancel Order", "Make Payment" >>>>> etc. are distinguishable as such to the choreography management >>>>> mechanism. >>>>> >>>>> Does this mean that REST, whose messages conform to a standardised >>>>> vocabulary (GET, PUT, POST, DELETE) that does not expose the >>>>> messages' business semantics, is incompatible with choreography? >>>>> >>>>> Any thoughts on this? >>>>> >>>>> Rgds >>>>> Ashley >
