Re: [soa-rm-ra] The Service Interface

[Rex Brooks <rexb@starbourne.com>]

Jeff, Frank, Everyone,

My $.02:

I also like the wiki definition of "one" the specific kinds of 
interface I think we need to specify in the RA.

I think we do need the "constraints" Frank is willing to accept, and 
those should include the two examples plus a verbal description of 
what implementation-independent components are required, e.g. the 
ability to provide bindings, not the particular binding mechanisms. I 
think the examples should be included in the RA. I also think that 
the ability to provide bindings for the appropriate MEPs should be 
highlighted in the examples.

Cheers,
Rex

At 4:27 PM -0700 10/26/07, Francis McCabe wrote:
>Jeff
>  That wiki defn is quite good!
>
>  The WSA defn includes 'all that you need' in order to 'make the 
>service work'. I think that that sentiment should be in our 
>definition also. That would mean that it would include the format of 
>messages.
>
>  You are also right about the interface being a subset of the 
>information and process model. I can see that there may be aspects 
>of both that are not needed to interact with the service; however, I 
>would also be quite OK with the idea of *constraining* information 
>and process models so that it *only* had information that was 
>relevant to the potential users of the service. This is especially 
>so if you include in users the people who may have to manage and 
>deploy the service.
>
>Frank
>
>
>
>
>On Oct 26, 2007, at 4:02 PM, Jeffrey A. Estefan wrote:
>
>>Folks,
>>
>>I'm in the process of crafting a UML component diagram for the 
>>Service Description artifact, but we need to nail down the notion 
>>of Service Interface before I proceed.  I don't want to indulge 
>>into endless debate here, I just want to know what is the minimum 
>>set of service implementation-independent things needed in order 
>>for a consumer agent to communicate with a provider agent (i.e., 
>>service).
>>
>>I happen to like Wikipedia's general definition of interface which 
>>states that "An interface defines the communication boundary 
>>between two entities, such as a piece of software, a hardware 
>>device, or a user."  Of course for the RA, we're talking about 
>>software interfaces that exist between separate software components 
>>that provide a mechanism by which the components communicate 
>>(consumer agents and provider agents/services) and not user 
>>interfaces per se.  We should perhaps extend that notion to 
>>physical interfaces as well, i.e., interfaces between hardware 
>>components because there is an evolving world of things like XML 
>>gateways out there.
>>
>>The WSA defines a service interface as follows:  "A service 
>>interface is the abstract boundary that a service exposes. It 
>>defines the types of messages and the message exchange patterns 
>>that are involved in interacting with the service, together with 
>>any conditions implied by those messages."  In terms of 
>>relationships to other elements, it goes on to say a service 
>>interface defines "the messages relevant to the service."  The 
>>explanation states "A service interface defines the different types 
>>of messages that a service sends and receives, along with the 
>>message exchange patterns that may be used."
>>
>>So is only a subset of the Information Model and Behavior Model 
>>enough, i.e., messages and MEPs?  What about service bindings (), 
>>endpoints, operations, faults, etc.  Do they have a role in the 
>>service interface.  In other words, are these examples of service 
>>implementation-independent things that are necessary the consumer 
>>agent to communicate with the provider agent/service?  In terms of 
>>the RM and RA, are there elements of Service Reachability at play?
>>
>>Whatever we agree on, we should be able to map to concrete examples 
>>(just to check our own sanity of course and not to include in the 
>>actual RA spec.) say one from the Web services world using WSDL 1.x 
>>and 2.0, and perhaps one from the CORBA IDL world.  Note that in 
>>the WSDL 2.0 world, the service interface defines what abstract 
>>"functionality" a Web service provides and the binding describes 
>>how to access the service.   In the RM and RA, we currently model 
>>Service Functionality separate from Service Interface.
>>
>>Interested in your thoughts.  Pragmatic ones, please!
>>
>>Cheers...
>>
>>- Jeff E., JPL
>>
>>
>>
>>
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Rex Brooks
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