Steve, On Nov 6, 2005, at 11:00 PM, Steve Ross-Talbot wrote:
> When they have the same behavior (i.e. when they are bisimilar). > That is one of the few good definitions, IMHO. What I find problematic (in terms of evolvability) is that the clients must know the service behaviour in order to decide if two services are substitutable. When clients must know service behaviour, the services cannot evolve without breaking the client's assumptions. I think type-based identity improves decoupling (and thus evolvability) because when I know I can submit my shoe order to service A as well as service B as long as they are both shoeOrderProcessors then these services can evolve as they like (as long as they stay true shoeOrderProcessors). All I need to now about Google is that it is a search engine...hypermedia will guide me through the state machine at run time every time. Is there anything about SOA in general that excludes type-based service identity? Jan > Cheers > > Steve T > > On 6 Nov 2005, at 09:16, Jan Algermissen wrote: > >> Question: >> >> what constitutes identity in SOA? When can a client consider two >> services to be identical? >> >> - when they have the same address? >> >> - when they have the same type (as in myService ---isInstanceOf---> >> ShoeOrderProcessor)? >> >> - when they have the same description? >> >> - unspecified; every SOA style software system must define identity >> for itself >> >> >> Jan >> >> >> >> >> >> >> >> On Nov 6, 2005, at 2:21 AM, JP Morgenthal wrote: >> >>> >>> Here's what I propose: >>> >>> A) Loose-coupling - every service is atomic, self-describing, >>> accessible, declarative, stateless and composite >>> B) Contracted - All services in an SOA are represented by a >> contract >>> that describes its inputs, outputs, access policies, QoS >>> requirements and >>> error handling procedures >>> C) Manageable - all services can be individually managed or >> managed >>> as a group >>> D) Versioned - multiple versions of the same service should >> be able >>> to co-exist to maintain backward compatibility in a changing >>> environment >>> E) Discoverable - services should be able to be discoverable >> at time >>> of execution. >>> F) Addressable - A service should be able to be uniquely >> identified >>> in a network >>> G) Distributed - Services in an SOA are separated by >> geographic and >>> machine boundaries and, therefore, must be good netizen >>> applications. That >>> is, they must be developed with the ability to recover from loss of >>> communications. >>> H) Point-to-Point - At any point in time one consumer uses >> one and >>> only one producer >>> >>> ------------------------------------ >>> Avorcor, Inc. >>> JP Morgenthal >>> Managing Partner >>> [EMAIL PROTECTED] >>> 12110 Sunset Hills Road, Suite 450 >>> Reston, VA 20190 >>> tel: (703) 648-1520 >>> fax: (703) 648-1523 >>> mobile: (703) 554-5301 >>> ------------------------------------ >>> >>> -----Original Message----- >>> From: [email protected] >>> [mailto:[EMAIL PROTECTED] On Behalf >>> Of Jan >>> Algermissen >>> Sent: Saturday, November 05, 2005 9:03 AM >>> To: [email protected] >>> Subject: Re: [service-orientated-architecture] Re: request for >>> pointers to >>> relevant information/documentation about SOA/SOC >>> >>> >>>>> >>>>> documents/publications related to SOA, starting from the basic >>>>> principles to more complicated stuff. >>> >>> I know this has propably been stressed too much, but simply cannot >>> resist :o) >>> >>> >>> >>> What are the basic principles of SOA? >>> >>> <duck/> >>> >>> Jan >>> >>> >>> >>> >>> >>> >>> >>> >>> Yahoo! Groups Links >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> ------------------------ Yahoo! Groups Sponsor -------------------- >>> ~--> >>> Get Bzzzy! (real tools to help you find a job). Welcome to the >>> Sweet Life. >>> http://us.click.yahoo.com/A77XvD/vlQLAA/TtwFAA/NhFolB/TM >>> -------------------------------------------------------------------- >>> ~-> >>> >>> >>> Yahoo! Groups Links >>> >>> >>> >>> >>> >>> >> >> >> _____________________________________________________________________ >> __ >> _ >> _______________ >> Jan Algermissen, Consultant & Programmer >> http://jalgermissen.com >> Tugboat Consulting, 'Applying Web technology to enterprise IT' >> http://www.tugboat.de >> >> >> >> >> >> >> >> >> >> SPONSORED LINKS >> Computer monitoring software >> Computer and internet software >> Free computer monitoring software >> >> YAHOO! GROUPS LINKS >> >> ▪ Visit your group "service-orientated-architecture" on the web. >> >> ▪ To unsubscribe from this group, send an email to: >> [EMAIL PROTECTED] >> >> ▪ Your use of Yahoo! Groups is subject to the Yahoo! Terms of >> Service. >> >> > > > > > > ------------------------ Yahoo! Groups Sponsor -------------------- > ~--> > Fair play? Video games influencing politics. Click and talk back! > http://us.click.yahoo.com/T8sf5C/tzNLAA/TtwFAA/NhFolB/TM > -------------------------------------------------------------------- > ~-> > > > Yahoo! Groups Links > > > > > > ________________________________________________________________________ _______________ Jan Algermissen, Consultant & Programmer http://jalgermissen.com Tugboat Consulting, 'Applying Web technology to enterprise IT' http://www.tugboat.de ------------------------ Yahoo! Groups Sponsor --------------------~--> Fair play? Video games influencing politics. 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