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Subject: RE: [soa-rm] Reference Architecture
> That brings up another question. Forgetting about > contradictions between the reference architectures for a > moment, could a given concrete architecture be generated from > more than one reference architecture. I would say absolutely yes. In fact, I briefly touched on this in the presentation that Rebekah and I gave last Tuesday, specifically when speaking about the associations between SOA-RM and the DRM. I mentioned the general notion of taking 2 reference models and extracting various aspects of each of them, to form a new entity (thing). The same notion may apply to reference architectures as well. The example I gave was a car that could fly above the highway in rush-hour traffic and get to the exit that is only 50 feet away from them (us DC-area folks are thinking about the Capital Beltway of course). Such an invention would have features of both a car and a plane, though not all features of both. Joe Joseph Chiusano Associate Booz Allen Hamilton 700 13th St. NW, Suite 1100 Washington, DC 20005 O: 202-508-6514 C: 202-251-0731 Visit us online@ http://www.boozallen.com > -----Original Message----- > From: Michael Stiefel [mailto:development@reliablesoftware.com] > Sent: Sunday, January 29, 2006 7:24 PM > To: frankmccabe@mac.com; soa-rm@lists.oasis-open.org > Subject: Re: [soa-rm] Reference Architecture > > Agreed that the appropriate requirements should be part of > the RA. Also agreed that the requirements could vary in their > "concreteness". > > To use our housing example, we could have any one of the > following requirements in the RA: > there has to be an eating area > the eating area may or may not have room for dining > the eating area must have a dining area and either a > stove or a microwave > the eating area must take up between 10% and 20% of > the are of the floor it is on > etc. > > It almost seems that the RA could be a sort of abstract BNF > or some set of production rules. > > That brings up another question. Forgetting about > contradictions between the reference architectures for a > moment, could a given concrete architecture be generated from > more than one reference architecture. > > For example, a Queen Anne style building originally borrowed > from pre-Georgian and late Medieval style buildings. It > eventually developed into a pastiche of various influences. > > Michael > > At 07:55 PM 1/26/2006, Francis McCabe wrote: > >Right. > >Although I think that the requirements need not be > completely concrete > >in a reference architecture. Also I think that we need to > ensure that > >the requirements we adopt are an explicit part of the RA itself. > >One other thing, there are requirement of an architecture and > >properties of an architecture. So I think that the > appropriate logic is: > > > >There are requirements a,b and c. These are predicates, if you will, > >that must be satisfied by the architecture. > >There are properties p, q and r. If these properties hold > then a,b and > >c will be satisfied. It may not be provable that p,q and r will give > >you a, b and c. But properties are measurable. > >Then there are mechanisms (modules, patterns, relationships > whatever) > >that, in combination, exhibit properties p, q and r. > >Then you are done! > > > >E.g., "the architecture shall be securable" is a reasonable > >requirement. We assert that proper authentication and auditing will > >result in a secure architecture. (Not by itself provable of course.) > >Then in an architecture in which agents must authenticate > themselves, > >and supply authentication tokens to an escrow for each communication > >then we have established a mechanism that gives us our required > >properties and have a secure architecture. > > > >Frank > > > > > >On Jan 26, 2006, at 6:53 AM, Michael Stiefel wrote: > > > >>Frank: > >> > >>Fair enough. > >> > >>Let me see if I understand you correctly. A reference architecture > >>states principles such as: > >> > >>Given concrete requirements a and b abstract mechanism x > will be one > >>possible way to salsify it. > >>Given concrete requirement c, abstract mechanism y will be the only > >>way to satisfy it. > >>Given concrete requirements d and e, a you use abstract > mechanisms w > >>and z to satisfy it. > >>Given concrete requirement f, a relationship between model > elements q > >>and r is the only way to satisfy it. > >> > >>Michael > >> > >> > >>At 11:11 PM 1/25/2006, you wrote: > >>>Michael: > >>> I have to confess that I don't much like this > definition. It gives > >>>no guidance or expectation as to what an RA will do for > you. That is > >>>why I used the phrase mechanisms - I want to be able to inform > >>>architects how to build something that will work. > >>>Frank > >>> > >>>On Jan 25, 2006, at 6:58 AM, Michael Stiefel wrote: > >>> > >>>>Here is a link discussing using reference architecture within the > >>>>RUP framework: http://www-128.ibm.com/developerworks/rational/ > >>>>library/2774.html > >>>> > >>>>I am not advocating the RUP framework, but they seem to have a > >>>>definition of a reference architecture that could serve as a > >>>>starting point: > >>>> > >>>>A reference architecture is a resource containing a > consistent set > >>>>of architectural best practices for use by all the teams in your > >>>>organization. > >>>> > >>>> > >>>>As a set of patterns it is reasonably abstract, yet > concrete enough > >>>>to help develop specific solutions. > >>>> > >>>>Michael > >>>> > >>>>At 12:33 AM 1/14/2006, you wrote: > >>>>>The time has come to start considering the development of a > >>>>>Reference Architecture. > >>>>> > >>>>>The TC agreed to establish a sub-committee to pursue this, so we > >>>>>will be called the SOA RM TC RA SC ! > >>>>> > >>>>> The first item of business is to develop a statement > of purpose. > >>>>> > >>>>> One suggestion is: > >>>>> > >>>>> To develop, in accordance with the SOA RM TC Charter, > a reference > >>>>>Service Oriented Architecture. > >>>>> > >>>>> Definition: A reference model that is mapped onto software > >>>>>elements that implements the functionality defined in > the reference > >>>>>model. > >>>>> www.sei.cmu.edu/architecture/glossary.html > >>>>> > >>>>> Definition: A reference architecture is an abstract set of > >>>>>mechanisms and relationships that models a predetermined set of > >>>>>requirements. > >>>>> McCabe 2006 > >>>>> > >>>>> Keywords: abstract, mechanisms, model, requirements. > >>>>> > >>>>> A reference architecture can be to guide the realization of > >>>>>implementations where specific properties are desired of the > >>>>>concrete system. > >>>>> > >>>>> To initiate the discussion, some questions suggest themselves: > >>>>> > >>>>>1. What requirements should be captured in a reference > architecture > >>>>>2. What mechanisms are required to realize those requirements 3. > >>>>>What is the relationship between the Reference Model and the > >>>>>Reference Architecture 4. What additional concepts (if any) to > >>>>>those captured in the Reference Model are necessary to > develop an > >>>>>RA. > >>>>> > >>>>> Immediate steps > >>>>>1. To agree on a statement of purpose 2. To collect requirements > >>>>> > >>>>>Let the fur fly! > >>>>> > >>>>>Frank McCabe > >> > >> > > > > >
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