2008/9/1 Michael Poulin <[EMAIL PROTECTED]>: > Steve, would it be proper understanding of your splendid example if I say > that each participant indicated "the next stages of the process flow" that > addressed its business goals?
Yes. Or more explicitly indicated the interactions that would help the participants reach the mutual goal. Basically the process would be one of three things. Firstly a case where there are a number of async options which can be called repeatedly (information sources and triggering events) and secondly a case where things must have a defined order (e.g. a fraud check before a credit card payment). Where it got clever was the third case with these being exchanged between participants often with one side having the fixed process and the other the eventing, this gave some good performance boosts as it reduced the amount of network traffic by shifting the processing onto the other end. This third case was in effect "run this on my behalf". > > I can imagine a policy/rule that might allow such dynamic construction of > the process. However, if participants were really independent (?), who did > you resolve potential situations of conflicts of interests (between just > received response from participant A and other participants that were not > called yet but assumed to be called (by BPEL) if participant A would not > change the process flow )? Which is why its important for the goal to be mutual. In something like vendor managed inventory you have such a thing. Thus there is no reason to not follow the defined process. Despite what others have claimed however its normal in enterprise and B2B environments for the different sides in a negotiation to be active participants in the whole project with all of the rules, and penalties, being laid down to ensure conformance. Steve > > - Michael > > ----- Original Message ---- > From: Steve Jones <[EMAIL PROTECTED]> > To: [email protected] > Sent: Monday, September 1, 2008 12:33:10 PM > Subject: Re: [service-orientated-architecture] Re: Distinction between > "Choreography" and "Orchestration" > > 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] com>: >> 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 <jones.steveg@ gmail.com> >> 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] com>: >>> >>>> 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] com> >>>> 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] net> >>>>> To: service-orientated- architecture@ yahoogroups. com >>>>> 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 >> > >
