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Subject: RE: [soa-rm] Service Contract
I understand what you are saying. My concern is that when people see metadata expressed using UML, they will then proceed to use UML for the rest of the analysis. I also fully agree that the RM should not constrain ones choice. I only picked SOAD because it illustrated the limits of UML for understanding service orientation. I also share your concern about being careful about what we mean with the term loose-coupling. Michael At 04:52 AM 4/27/2005, George Ntinolazos wrote: >The diagrams represent the abstract elements of the Service >Contract(operations, data types/messages etc). They try to capture the >metadata associated with Platform Independent contracts, to use an MDA term. > > >The example model defines the abstract syntax and semantics for the service. >It does not specify how the contract is realized; it can be >mapped/transformed to a specification language like WSDL, Java or IDL. Based >on the choice of a specification language one can achieve different levels >of loose-coupling. (yet another subject is what do we mean by loose >coupling: loose-coupling at technology, protocol, application, semantic >level to name a few different types) > >How one identifies the services, the architectural layers etc is a >development process question. IMHO, the RM should not attempt to constraint >the choice here. IBM's SOAD might be one example. I would also point you to >existing methodologies like Business Component Factory (Herzum, Sims), >Convergent Architecture (Hubert) and UML Components (Cheesman, Daniels). >Although these methodologies emphasize Component based provisioning, their >specification (or analysis) steps focus on large grain software services >that represent 'business elements' (a process, a resource, or an >organization unit). > >Cheers > >George > > > >-----Original Message----- >From: Michael Stiefel [mailto:development@reliablesoftware.com] >Sent: 27 April 2005 02:12 >To: Don Flinn; George Ntinolazos >Cc: 'SOA-RM'; 'Duane Nickull' >Subject: Re: [soa-rm] Service Contract > >I agree with this. > >The limitations of object modelling for service orientation is the reason >that IBM is trying to develop SOAD (Service Oriented Analysis and Design). >Their initial paper on this concept >(http://www-128.ibm.com/developerworks/webservices/library/ws-soad1/) >discusses how to group loosely coupled services on the basis of their >related behavior and processes instead of the encapsulated behavior and >data of tightly coupled business objects. > >Michael > >At 11:58 AM 4/26/2005, Don Flinn wrote: > >George > > > >The diagrams in your attachment depict services and semantics in terms > >of operations and parameters. IMHO this is a carry over from the > >original OO orientation of UML, which implies rigid, inflexible API > >based services. Such an approach goes against the spirit of SOA, which > >IMO should be based on loosely coupled principals. While one could > >design an SOA based on rigid APIs, I for one would not do so. I also > >question whether the RM should encourage the API model. I, personally, > >would go further and discourage the API based approach in a Service > >Oriented Architecture. > > > >Don > > > >IMHO this is the legacy from UML and does > > > >On Tue, 2005-04-26 at 12:52 +0100, George Ntinolazos wrote: > > > Hi all > > > > > > Please find attached a document with notes re: Service Contracts > > > > > > Cheers > > > > > > George > > > > > > ___________________________________________ > > > George Ntinolazos BSc(Hons), MSc, MBCS > > > > > > Product Director > > > Strata Software Ltd. > > > Office: +44 (0)1483 422515 > > > Mobile: +44 (0)7966 652063 > > > www.stratasoftware.com > > > Best Practice for Service-Oriented Architectures > > > > >-- > >Don Flinn > >President, Flint Security LLC > >Tel: 781-856-7230 > >Fax: 781-631-7693 > >e-mail: flinn@alum.mit.edu > >http://flintsecurity.com
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