On Thu, Jul 9, 2009 at 8:25 AM, Mike Edwards < [email protected]> wrote:
> Hi folks, > > I am writing as one of the committers on Apache Tuscany, which is using ODE > to provide SOA components using the BPEL langage, combined with other > components written in many other languages. > > One of the capabilities that Tuscany provides, through its implementation > of the Service Component Architecture (SCA) specification for BPEL, is the > capability to provide "external initialization" of BPEL variables. I am > interested in getting a clean implementation of this capability with ODE. > > So, first, how is this capability described? > > The SCA BPEL spec has an extension attribute that is used on a BPEL > variable declaration to indicate that its value should be initialized from > SCA metadata, like this: > > <variable name="testName" type="xsd:string" sca-bpel:property="yes"/> > > ...where sca-bpel is the prefix referring to an SCA namespace: > > xmlns:sca-bpel="http://docs.oasis-open.org/ns/opencsa/sca-bpel/200801"; > > > The related SCA metadata might look something like this: > > <component name="TestClient"> > <implementation.bpel process="bpel:ClientInterface_0002"/> > <service name="TestInvocation"> > <interface.wsdl interface=" > http://test.sca.oasisopen.org/#wsdl.porttype(TestInvocation)<http://test.sca.oasisopen.org/#wsdl.porttype%28TestInvocation%29>"/> > > <binding.ws/> > </service> > <reference name="reference1" target="TEST_ASM_4001Component1/Service1" /> > <property name="testName">ASM_4001</property> > </component> > > It's that <property/> element that drives the initializer value for the > variable within the BPEL process. (Note - this is a trivial case, SCA allows > for much more complex setting of data values...) > Note that this DOES NOT imply that the variable is an "external variable" > in the ODE sense - other than the initialization, the variable is a standard > BPEL variable. > > > At the moment, there is no clean way of performing this initialization > using ODE. The latest version of ODE does support the concept of > initializer values - what we need is to have some "external code" invoked at > the right time to fetch the data value and set the value into the BPEL > variable. > > I'm interested to hear if you would be willing to consider adding a few > extra capabilities to ODE to enable this feature. I believe that much of > what is needed is already in the latest ODE code, but it will need some > extra code to organize things. I think that it might be along these lines: > > 1) Tweak to the BPEL Compiler code to allow recognition of the > sca-bpel:property extension attribute and for the compiler to generate code > that will do initialization of the related variable, but through the > invocation of some external extension code at runtime. > > 2) Tweak to the runtime code to allow for the invocation of external > extension code during variable initialization, and for that code to be able > to assign a value to the variable. > > > Comments welcome - please tell me if I'm being insane here, for example! I > would expect the Tuscany folks (probably me!) to write the actual external > extension code called at runtime, but the plug points would have to be in > the core ODE code, both for the compiler and for the runtime. > Hey Mike, the approach sounds reasonable and your two steps are correct. About the addition of this feature, I personally doubt I'll have time for this. But if anybody is willing to step up, please be my guest. Cheers, Matthieu > > > Yours, Mike. >
