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Subject: RE: [soa-rm] David Linthicum Says: "ESB versus Fabric.Stop It!"
> -----Original Message----- > From: Duane Nickull [mailto:dnickull@adobe.com] > Sent: Tuesday, May 24, 2005 2:56 PM > To: Michael Stiefel > Cc: soa-rm@lists.oasis-open.org > Subject: Re: [soa-rm] David Linthicum Says: "ESB versus > Fabric.Stop It!" > > Endpoints are part of a service description IMO. > Orchestration of multiple services is out of the scope of > the core RM, much the same way as how multiple houses are > positioned next to each other in a grid layout is > un-necessary in order to define a RM for house. > > A service or house do not have to exist amongst multiple > houses in order to be services/houses. Which brings us back to what I believe is the single most important question for us to answer: Does one service constitute a SOA? Or are 2 or more services required? If 2 or more services are required, then it seems to me that in order to call something a *SOA* reference model, the notion of multiple services must be incorporated - as that is the minimal amount of information necessary to *effectively* represent/model the "targeted entity" (which is SOA) for the intended audience. If one service constitutes a SOA, this implies that a SOA may have more than one service. It then seems to me that one has a choice for their RM: include only a single service in the model, or include multiple services. The question then becomes which approach enables the most effective representation for the intended audience. So as you see, I believe everything flows from this single most important question. Joe Joseph Chiusano Booz Allen Hamilton Visit us online@ http://www.boozallen.com > Duane > > Michael Stiefel wrote: > > > Could we then conceive of endpoints and orchestration in such a > > fashion? Or is the critical point aspect or attribute in which case > > endpoint qualifies, but orchestration does not. > > > > To make a grammatical analogy, the RM defines a substantive, and > > therefore adjectives (aspects and attributes) are part of > the RM, but > > verbs (actions) are not. > > > > (side note: I know verbs have aspect, but we are not using the term > > that way). > > > > Michael > > > > At 02:34 PM 5/24/2005, Duane Nickull wrote: > > > >> Since Structural Integrity is an aspect of all houses, it could be > >> part of a RM as an abstract concept. Even if you do not > explicitly > >> design a house to have a certain set of structural integrity > >> parameters, it still does. It is not a component itself, just an > >> aspect or attribute. > >> > >> Duane > >> > >> > >> Michael Stiefel wrote: > >> > >>> I thought of structural integrity in terms of the entire > house, not > >>> just a wall, but I think your point remains the same. > >>> > >>> Granted that each architecture needs to specify its structural > >>> integrity, but shouldn't the RM have the concept of structural > >>> integrity since it is an abstract concept shared by all RAs. > >>> > >>> Michael > >>> > >>> At 02:06 PM 5/24/2005, Duane Nickull wrote: > >>> > >>>> The RM does not necessarily have to get into cardinality > rules IMO, > >>>> unless they are very obvious. In the case of a house, > you may not > >>>> make consistent rules stating that every house has to > have at least > >>>> three walls since a wall can be curved or any number of > walls from > >>>> 3 up. You may be able to infer from the relationships > that there > >>>> is a certain cardinality if the RM for a house said that > each room > >>>> has one door. > >>>> That would declare an association between the number of rooms to > >>>> the number of doors. > >>>> > >>>> Structural integrity is an aspect of a wall, which must be > >>>> specialized for each architecture based on a number > criteria. The > >>>> RM declares what the wall is and its' purpose, the architect has > >>>> the job of specifying the actual walls to be used for each > >>>> architecture and ensuring they map back to requirements. > >>>> > >>>> You are right - analogies are not definitions, however I > have found > >>>> them very useful in conveying the meaning. > >>>> > >>>> Duane > >>>> > >>>> Michael Stiefel wrote: > >>>> > >>>>> Does the RM understand that some of the concepts are unique and > >>>>> some multiple (without an exact number, you could have one > >>>>> circular wall, 3 walls, 4 walls, etc.)? > >>>>> > >>>>> Using your analogy, how does the RM deal with concepts such as > >>>>> structural integrity. Structural integrity would apply to all > >>>>> house RAs. In my way of thinking concepts such as endpoints or > >>>>> orchestration are analogous to this. > >>>>> > >>>>> In the analogy I would see the reference architecture > as Colonial > >>>>> American Reference Architecture, or even more specifically > >>>>> Colonial American Cape Ann, or Colonial American Greek Revival > >>>>> reference architectures. > >>>>> > >>>>> Analogies are useful, but they are not definitions. > >>>>> > >>>>> Michael > >>>>> > >>>>> At 12:56 PM 5/24/2005, Duane Nickull wrote: > >>>>> > >>>>>> RA means Reference Architecture. As per the previous > emails on > >>>>>> this subject, it is a generalized architecture. > >>>>>> > >>>>>> The relationship is that architects use a RM as a > guiding model > >>>>>> when building a RA. > >>>>>> > >>>>>> For example, if you are architecting a house, an RM > may explain > >>>>>> the concepts of gravity, a 3D environment, walls, foundations, > >>>>>> floors, roofs, ceilings etc. It is abstract however. > There is > >>>>>> nothing specific like a wall with measurements such as 8 feet > >>>>>> high. Note that the RM has only one each of these things - it > >>>>>> does not have 4, 16, 23 walls, just one as a concept. > >>>>>> The architect may uses this model to create a specific > >>>>>> architecture for a specific house (accounting for such > things as > >>>>>> property, incline, climate etc) or an architect MAY > elect to use > >>>>>> it to build a more generalized reference architecture. The > >>>>>> latter is often done by architects who design houses. > When they > >>>>>> sell a house, they must often re-architect the RA for specific > >>>>>> implementation details such as incline of land, > climate, facing > >>>>>> the sun etc.. > >>>>>> > >>>>>> So why do we need a RM? Simple - we now have logical > divisions > >>>>>> amongst the components of a house and what they mean. > That way, > >>>>>> when a company says " we are a flooring company..", that is > >>>>>> meaningful since we all know what that means. The > same applies > >>>>>> to a roofing company. Without the basic consensus on > the logical > >>>>>> divisions, a roofing contractor may also try to include the > >>>>>> ceiling and walls as part of his offerings. > >>>>>> That would not work and not allow the general > contractor to build > >>>>>> a house very easily since there may not be consensus upon the > >>>>>> division of labor and components to build the house. > >>>>>> > >>>>>> Do you guys think an explanation of this nature may be good to > >>>>>> include in the introduction section? > >>>>>> > >>>>>> Duane > >>>>>> > >>>>>> Chiusano Joseph wrote: > >>>>>> > >>>>>>> What is an RA? What is the relationship between an RM > and an RA? > >>>>>>> What is > >>>>>>> the RM->RA path for SOA? > >>>>>>> > >>>>>>> Matt also submitted last week (I believe) that we may > not even > >>>>>>> need an RA. How should that change our notion of RM, > if at all? > >>>>>>> > >>>>>>> Joe > >>>>>>> > >>>>>>> Joseph Chiusano > >>>>>>> Booz Allen Hamilton > >>>>>>> Visit us online@ http://www.boozallen.com > >>>>>>> > >>> > > > > >
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