[news.eclipse.stp.sca-tools] Re: Service term in SCA

[Stephane Drapeau <Stephane.Drapeau@xxxxxxx>]

Michael Gebhart a écrit :
> Hi,
>
> I have a problem with the term of service in SCA. What is meant with a 
> service here? Is it a service in terms of a service that should be 
> published within a service inventory (as for instance UDDI) that other 
> interested parties can use it? Should these services be designed that 
> they can be used from other parties too?
>
> Or is this service for internal use only? This would mean that it is 
> simply an interface for a component?
>
> Best regards
>
> Michael

Hi Michael,

I think that your misunderstanding is prompted by the fact that SCA 
wants to unify 2 visions of distributed systems: (a) the 
architecture-based and (b) the service-oriented visions.

In vision (a), a distributed system is organized as an architecture 
built as an assembly of components with well defined interfaces. In 
vision (b), a distributed system is organized as a set of independent 
services used by different clients. Moreover, the main idea behind the 
term service is the possibility to re-use them (services must be 
designed for that : autonomy, loose coupling, stateless,...) and to 
aggregate them to construct other services. You can find more 
information here [0] (page 5) and an interesting article about service 
granularity here [1].

So, to answer your question, SCA services
- can be used by other interested parties : a service promoted at the 
composite level with a web service binding can be used by non SCA clients,
- can be used to construct an assembly of components. In this case, the 
service can or not (internal use only) be promoted outside the composite.

Regards,

Stephane Drapeau
Obeo

[0]: 
http://www.scorware.org/projects/rsc/deliverables/SCOrWare-L1-Specifications-V2-0-20090414_pdf?action=download&nodecorator
[1]: 
http://www.ibm.com/developerworks/webservices/library/ws-soa-granularity/