Ok, some sleep helped a little. I think the answer is to figure out
what SOA *really* is (as I believe was suggested eralier). (01)
Advance warning: I'm not really going to be talking about technology at
all, and I'm going to relate a few things which some may find a bit
tangential. However, I think if we can solve this, the rest is going to
be a lot easier. (02)
In 1722 Benjamin Franklin wrote (as Silence Dogood), “‘I have...found by
Experience, that it is impossible to talk distinctly without defining
the Words of which we make use’". (03)
So, that's the challenge. I think what we've seen thus far in the
discussion has really been somewhat affected by this issue. We're
making progress however. :) (04)
I think the most important term we've been using within this context is
the word 'community'. However, I think how it is understood (or not)
has massive implications about how successful our efforts will be with
SOA (industry-wide). For many years, I have had the intuitive feeling
that you can't legislate morality--it comes from something much more
fundamental than laws. Recently, from discussions on the XML-DEV
mailing list, I was directed to the writings of Aldo de Moor. In them,
I finally realized where my intuition originated: the concept of
legitimacy. (05)
Whitworth and de Moor define legitimacy as the common sense of fairness
which binds a community together [1]. As such, it is what allows the
community to grow, because continued acts in and towards the community
based on the same sense of fairness end up building trust amongst the
community. The more trust, the more openness, communication and
cooperation, and therefore the more benefit to the community as a
whole. Those of you familiar with Systems Thinking will recognize this
as a reinforcing system. (06)
However, when a member of the community violates the understood fairness
(legitimacy) of the community, one of two things happen. One outcome is
that it forever disrupts the community, and the community eventually
ceases to exist. There are a few examples of this in [1]. (07)
The other example of this outcome is that the community sees a need to
more clearly state these shared concepts of legitimacy. In society,
this is done by passing laws. In computer systems, it is done using
access control and by introducing other design constraints. (08)
In society in the large, option one really isn't a runner, so more often
than not, the second one is chosen. I suppose, in the interests of
completeness, I should point out that there's a third option, war, but I
don't think it fits into the current discussion. (09)
Assuming that the second option: making laws to enforce the understood
legitimacy traits of society, is chosen, this eventually leads to an
evolved framework defining various aspects of legitimate behavior within
the community. It works, because they are, by definition, *legitimate*,
i.e. fair. People who understand legitimacy in a community normally
don't have to be told what is right and what is wrong for every decision
they make. When implemented properly, everyone's actions generally
reinforce the legitimacy of the community, thus contributing to the
reinforcing system described above. I have written about this
previously in the context of enterprise security [2], but not in this
pure of a form. (010)
Of course, there are always participants in a community who don't
subscribe to the same legitimacy principles. That's where the laws kick
in and either prevent them from doing any damage, or reactively attempt
to prevent others from following a bad example. Still, if coercion is
the only option, this approach will eventually break down as described
in [2] due to the trait of tolerance. (011)
When the system is working correctly, very little interaction with the
codified principles of legitimacy within the community (laws) is
necessary by the participants. I'm sure not many of us could, from
memory, list the exact details of the laws that exist in a locality, let
alone on a larger scale such as a state or a nation, but that fact does
not generally prevent us from going about our daily business. Thus, I
posit that this is primarily because we subscribe to the legitimacy
principles of the communities in which we participate. (012)
If this is accepted, then what are the outcomes of the community? The
main one is that the members of the community are fairly autonomous.
Either implicitly or explicitly, they understand the context in which
they operate, altering their behavior to conform to the legitimacy
principles required for the various communities in which they
participate. Before long, this alteration happens automatically,
without conscious thought from the participants. Do you talk to your
mother the same way you talk to your friends? (I do, because I have a
cool mom, but most people probably don't. This behavior is an example
of what I'm talking about). (013)
One of the largest benefits of autonomy is the ability to work
co-operatively to accomplish a larger goal. However, this "directed" or
"cooperative autonomy" is only effective if everyone fully understands
what they are supposed to do and have the ability to do it. (014)
Bringing all this back a little closer to the topic at hand, the degree
of autonomy in a system is directly proportional to the scalability of
that system. I have elaborated on this concept from a messaging point
of view [3]. However, what struck me this morning when I was thinking
about this conversation was this relationship: (015)
scalability => autonomy => legitimacy (016)
Or, that in a system, scalability implies a certain amount of autonomy,
but that this autonomy is only possible if the autonomous entity has an
awareness of and subscription to the legitimacy principles of the
community in which they are participating. (017)
Bringing this back even closer to the current discussion, my use of the
road metaphor in the earlier mail was a better of example of this
thought than I realized. I said: (018)
> > The SOA part kicks in when I can drive from McD's, to BK, to Wendy's to
> > Arby's, or wherever, and send the same message and expect the same
> > response. In W3C-speak, ordering food is the abstract service and each
> > of the fast food places is a concrete implementation of that service (an
> > agent). The SOA tells me how I can get from point to point, what rules
> > I must follow, and maybe even gives me directions. It may also allow me
> > to get fuel, buy a candy bar or even a newspaper--if those messages
> > existed and there was an agent implementing a service providing them. (019)
Relating the architecture of the SOA back to the society in which we
live and adding in the concept of legitimacy, the traffic laws say where
and when we can drive from point to point. Mostly, people obey these
laws, but I would say that the most fundamental ones (speed limits don't
count here :D) are "obeyed" less because they are laws, but more because
they resonate with our innate sense of fairness. (020)
So, these are the reasons that I actually don't agree with you that
requestor/provider roles/concepts are too low-level within the context
of the SOA. To me, these provide the power of the SOA. This leads me
to conclude that the architectural constraints of the SOA define the
legitimacy principles of the environment, in a similar manner to the way
Whitworth and de Moor say that the programmer is ultimately defining the
legitimacy principles of the social interaction systems they design and
build [1]. (021)
If a framework for what is and is not legitimate within the SOA
community is defined, the participants within that community are free to
be autonomous within that community as long as they follow the rules.
This autonomy within the community allows the community to scale in the
same manner as the Internet [3]. (022)
Note as well that these rules of legitimacy are not restricted to the
software agents acting within the community. It also applies to the
manner in which the human participants interact with each other and with
the software agents as part of the community. This is a model that has
been proven to work (to various degrees) in both computer systems (the
Internet) and society. Managing autonomy is harder than some of the
alternatives, however it is the only way to provide sufficient
scalability within the community to accomplish anything meaningful. The
balancing system at work here is dealing with those that don't conform
to the legitimacy principles. Once these cases are identified, steps
are taken to augment the framework, and life goes on. (023)
This is exactly what happens between government and the governed. If
one sees the other violating the community's legitimacy principles past
a tolerance point, action is taken--in either direction--to re-balance
the environment. I believe that this is the model that SOA must follow
if it is to be successful. (024)
In large deployments with hundreds of services, thousands of people and
millions of messages, it has to have the ability to adapt on its own
behalf--within the framework that defines the architecture of the
community. When this behavior does not occur, the scalability, and
therefore the effectiveness of the architectural style, becomes
constrained. If that happens, we'll be here in another 5-10 years
arguing about the "next big thing" vs. "the last big thing" because we
will have reached a point where the SOA model is no longer useful. (025)
As the Internet has proven, I think it is possible for this type of
community architecture to exist. We just can't repeat some of the
mistakes of the Web which did not consider the legitimacy concerns of
the participants and which has led to some of the issues we have today's
society (e.g. widespread identity theft and fraud). (026)
By allowing the business processes and roles (as you use the term) to
fully participate in this community *as peers*, I believe that SOA is an
architectural style which can achieve the business needs of
collaboration, integration and agility. We just have to create the
right community. (027)
ast (028)
[1] http://www.starlab.vub.ac.be/staff/ademoor/papers/bit03.pdf
[2] http://atownley.org/published/2005/06/ISB1005AST.pdf
[3] http://atownley.org/2006/03/self-directed-messages-the-key-to-scalable-soa/
On Wed, 2006-03-29 at 18:49, Cory Casanave wrote:
> Andrew,
> Thanks for your comprehensive response, we are certainly attempting to
> realize the same goals, perhaps with slightly different terminology and a
> few different conclusions. I'm going to pick out a couple of your
> statements to reply to directly...
> >
> > SOA is not about distributed objects.
> >
> Absolutely and violently agree. It actually disturbs me that you think I
> think it is, I will have to look back on the prior communications to see
> where this came from.
> >
> > Just to clarify some of these key differences a bit more. The way I see
> > SOA is the environment in which a service exists. This service can be
> > big or small, but it provides the same sort of granularity, regardless
> > of the business process being achieved--it is a business service.
> >
> Absolutely agree - SOA is the business architecture (where the business is
> understood as providing and using business services). This business
> architecture MAY be realized with distributed objects or with an event
> service or with paper flowing between in/out baskets.
> We MAY map the business interactions to one of these technologies. People
> who DO think if architecture in terms of technology services are looking for
> something like an Corba-IDL or WSDL interface - to map business interactions
> to this paradigm we talk about "service interfaces" as the way these
> paradigms MAY be used to REALIZE the SOA architecture.
> >
> > For example, you (the requester) are hungry. Not knowing any better,
> > you pull through the drive-up at McDonald's (the provider) and order a
> >
> Don't agree - the requester/provider mindset if to low-level for business
> interactions - it really comes from the OO think we are both trying to rise
> above. Business interactions are inherently bi-directional, asynchronous
> (as you have said) and long-lived. Information flow may be initiated from
> either side, within the constraints of the choreography of that interaction.
> They are frequently complex and composed of finer grain interactions. There
> are roles in these interactions and you can frequently identify one as the
> "initiator", but expecting a request/reply paradigm is not business centric.
> As said above, we may MAP the business centric interaction to one or more
> request/reply service interfaces.
>
> Since you took the time to write down some great definitions I have provided
> some corrections (since you said they were my definitions).
> >
> > community -- a pair of roles interacting for some purpose
> >
> community -- a set of roles interacting for some purpose
>
> > role -- a task or responsibility within a community
> >
> role -- a logical grouping of a set of responsibilities within a community
>
> > interaction -- the means of communication between a role
> >
> interaction -- the means of communication between actors playing roles
>
> > community contract -- the constraints and manner of interaction between
> > a pair of roles using specified service interfaces
> community contract -- the purpose, constraints and manner of interactions
> within a community
>
> > Specification -- codification of a given community contract
> Specification -- codification of a given contract
>
> >
> > SOA -- an architecture consisting of the following core elements:
> > - people and organizations
> > - roles and responsibilities
> > - interactions between roles
> > - community contract
> >
> >
> SOA -- an architectural style for achieving collaborative work that can be
> specified using a community contract containing the following core elements:
> - roles and responsibilities
> - interactions between roles
> - business rules and constraints
> - a model (or ontology) of the domain
>
> > service interface -- a set of methods exposed by a distributed object
> > (as exemplified by middleware technologies like RMI/IIOP, CORBA, DCOM,
> > .NET remoting and SOAP)
>
> This is ok, but is a possible derivative of the SOA, not the subject of the
> SOA.
>
> >
> > collaboration -- interactions between roles to realize a business
> > process
> >
> > integration -- the combination of all of the elements defined by the SOA
> > (above) to enable a collaboration
> >
> > interoperability -- the level to which a role and service interface
> > conform to the interaction contract of the community within a
> > collaboration (implying some sort of shared context between the two
> > roles)
>
> Interoperability - the ability for business units, people or systems to
> exchange information in support of a common purpose.
>
> >
> > There are also a few terms that I'm not sure I understand from your
> > usage.
> >
> > agility -- this is a term which has a number of different meanings,
> > depending on your context. Can you explain to me what you mean by: "how
> > things work together for a common purpose while retaining _agility_"?
>
> Agility - the ability for new objectives, whether driven by business,
> mission or technology, to be realized quickly and inexpensively.
>
> >
> > architecture -- I think it's the environment in which all of the above
> > interactions take place, but I'm not really 100% sure from your usage.
> >
> Architecture - the design of systems; where systems may be organizational,
> legal, physical, processes or processing systems.
>
> -----------
> So, now it is clear we are BOTH crazy! I wonder if anyone else is still
> listening?
>
> -Cory
>
> > -----Original Message-----
> > From: soa-forum-bounces@xxxxxxxxxxxxxx [mailto:soa-forum-
> > bounces@xxxxxxxxxxxxxx] On Behalf Of Andrew S. Townley
> > Sent: Tuesday, March 28, 2006 8:21 PM
> > To: Service-Oriented Architecture CoP
> > Subject: Re: [soa-forum] Business Need for SOA (Was SOA Semantic
> > Variation )
> >
> >
> > Hi Cory,
> >
> > After spending considerably more time on this today than I planned (when
> > it wasn't interrupted by "real" work and meetings), I honestly think
> > we're trying to accomplish the same goals. However, I think there are
> > currently two things which are possibly preventing clearer
> > communication.
> >
> > First, I think we have a bit of a terminology impedance which is
> > actually caused by the second: different starting points to SOA which
> > may have resulted in different perspectives. I believe that we can get
> > around these issues. What I will do is walk through some of the points
> > from the conversations over the last few days and then see if I managed
> > to catch the correct babel fish. However, there are still some things I
> > don't understand. Please forgive me if I'm just being thick.
> >
> > Based on your past published work [1,2,3], it is quite clear that you've
> > put a lot of thinking into where you are now. It's also pretty clear
> > that you've an extensive background with CORBA, UML and MDA.
> >
> > >From what you've said, I think that this has had a distinct impact on
> > how you view SOA. As you also said, you have seen and been a part of
> > several SOA solutions implemented in CORBA.
> >
> > If I understand what you've been saying over the last few emails, I
> > understand you to have the following definitions. I'm trying to nail
> > these down so that I'm sure what you mean, and I don't make the wrong
> > assumptions. I realize you may think I'm silly, but I really think it's
> > important to get straight.
> >
> > community -- a pair of roles interacting for some purpose
> >
> > role -- a task or responsibility within a community
> >
> > interaction -- the means of communication between a role
> >
> > community contract -- the constraints and manner of interaction between
> > a pair of roles using specified service interfaces
> >
> > specification -- codification of a given community contract
> >
> > SOA -- an architecture consisting of the following core elements:
> > - people and organizations
> > - roles and responsibilities
> > - interactions between roles
> > - community contract
> >
> > service interface -- a set of methods exposed by a distributed object
> > (as exemplified by middleware technologies like RMI/IIOP, CORBA, DCOM,
> > .NET remoting and SOAP)
> >
> > collaboration -- interactions between roles to realize a business
> > process
> >
> > integration -- the combination of all of the elements defined by the SOA
> > (above) to enable a collaboration
> >
> > interoperability -- the level to which a role and service interface
> > conform to the interaction contract of the community within a
> > collaboration (implying some sort of shared context between the two
> > roles)
> >
> > There are also a few terms that I'm not sure I understand from your
> > usage.
> >
> > agility -- this is a term which has a number of different meanings,
> > depending on your context. Can you explain to me what you mean by: "how
> > things work together for a common purpose while retaining _agility_"?
> >
> > architecture -- I think it's the environment in which all of the above
> > interactions take place, but I'm not really 100% sure from your usage.
> >
> >
> > If the above are right, or even close, I am now starting to see why
> > we've not been effectively communicating. :(
> >
> > I have done a few distributed computing projects as well, including some
> > with J2EE, CORBA, DCOM, .NET remoting and even some simple PDO things
> > under NEXTSTEP, XML-RPC and basic SOAP/1.1. So I am pretty well versed
> > with the paradigm.
> >
> > However, for the last 18 months, I've been implementing part of an
> > on-going SOA project based nearly exclusively on asynchronous
> > messaging. Based on this experience, and from reading everything I
> > could find about Web services, loose coupling, messaging, ESB and SOA,
> > I've come to the distinct conclusion:
> >
> > SOA is not about distributed objects.
> >
> > This is a pretty fundamental notion on which we seem to differ, but I'll
> > get to this in more detail as I go.
> >
> > Even though I'm not in 100% agreement with all it says, the W3C Web
> > Services Architecture [4], along with the W3C Web Services Glossary [5],
> > provide some useful, public definitions of terms. Like design patterns
> > enable communication of architectural design concepts between software
> > architects and developers, it is useful to have a baseline vocabulary
> > when discussing these things. And for everyone in the wings with a
> > semantics & ontology background, in case you were wondering, I haven't
> > missed the irony of that last sentence. :) I have tried to make the
> > terminology I use consistent with these definitions.
> >
> > I'll not go into all of them, but, to me, SOA is about "business"
> > services, but, like most things, what a "business" service actually is
> > depends on your point of view. If you're part of the process that
> > implements or is responsible for the desired outcome, you probably see
> > all of the little steps required to carry it out. If you are not part
> > of the process, you see the entire process as the service. This is just
> > natural human abstraction when they don't know or don't really care
> > about the details.
> >
> > For example, you (the requester) are hungry. Not knowing any better,
> > you pull through the drive-up at McDonald's (the provider) and order a
> > value meal, pay your money (send a complex message), pull up to the next
> > window and wait. Eventually, someone appears at the window with your
> > cholesterol bomb (receipt of a complex message), and you drive away
> > happy.
> >
> > This example seems to map to your definitions as the following:
> >
> > you (the requestor) -> role #1
> > McD's (the provider) -> role #2
> > you + McD's -> the community
> > hanging out your car window and talking -> the interaction
> > giving your order (including the money) + receipt of food -> community
> > contract
> > McD's window + your order + money + bag o food -> service interface
> > you ordering food from McD's -> collaboration
> > all of the above -> SOA
> >
> > Using this simple scenario again, here's how I would define the various
> > bits (more-or-less from the WSA/WSG):
> >
> > you -> the requestor
> > McD's -> the provider
> > ordering food -> the service
> > hanging out your car window and talking -> the transport
> > your order + money -> request
> > food -> response
> > send (any order for food + money); receive (food) -> service interface
> > roads + traffic laws + houses + shops + fast food places -> SOA
> >
> > Just to clarify some of these key differences a bit more. The way I see
> > SOA is the environment in which a service exists. This service can be
> > big or small, but it provides the same sort of granularity, regardless
> > of the business process being achieved--it is a business service.
> >
> > Also, services can be complex or simple. If we were in the pub, and I
> > asked you to go get me a burger, I'd give you my order plus some money
> > and get a burger back from you. I wouldn't care if you needed to go to
> > three different places to find what I wanted (except that it might be
> > cold).
> >
> > In this case, this would be a complex service (degenerate
> > case--specifically an intermediary) because you needed to do things on
> > my behalf. Later, I might also want to go to McD's directly, or I could
> > ask you again. If life was really good, I could use the same data in
> > both cases, e.g. both you and McD's would provide the same service
> > interface--enabling interoperability between service providers.
> >
> > The SOA part kicks in when I can drive from McD's, to BK, to Wendy's to
> > Arby's, or wherever, and send the same message and expect the same
> > response. In W3C-speak, ordering food is the abstract service and each
> > of the fast food places is a concrete implementation of that service (an
> > agent). The SOA tells me how I can get from point to point, what rules
> > I must follow, and maybe even gives me directions. It may also allow me
> > to get fuel, buy a candy bar or even a newspaper--if those messages
> > existed and there was an agent implementing a service providing them.
> >
> > The way I understand Web services and SOA is that they provide these
> > higher-level interfaces to business services, the invocation mechanism
> > and the messages exchanged. You get the interoperability because you
> > *can* place the same order at all those places and expect, with minor
> > variations, to get the same thing back. If you don't, they don't
> > implement the same service interface.
> >
> > I know these things sound very similar to what I suspect you understand,
> > but to me, they are very different. Messages are not parameters to
> > remote methods, and WSDL is not IDL. While you can use them that way,
> > this doesn't buy you anything over any other type of distributed objects
> > except unmolested access through port 80/443.
> >
> > The business processes are the interactions between the requester and
> > provider (through their agents implemented in software), if they're
> > RPC-style interactions, one-way interactions, or a complex, long running
> > choreography involving messages going from A -> B -> C -> D -> A as a
> > directed graph. The business processes can be modeled on any meaningful
> > level, but the type of centralized architectural view via MDA as I now
> > understand it (after today's research) isn't really there.
> >
> > Yes, you have auditing and governance as part of the architecture, but
> > it's as a peer to peer set of interactions between organizational
> > entities. Only the provider *needs* to have a service interface,
> > because the requester can send the request and then ask for the
> > asynchronous response. They aren't objects. Interoperability at that
> > point boils down to:
> >
> > - agreement or following a published business choreography
> > - agreement on the message data (or any transformations)
> > - standardized or commoditized transport
> >
> > If I want to book a flight, I provide the same information over the
> > phone, on the Web or in person to a travel agent. They all implement
> > the same service interface, but the transport and agents are different.
> >
> > To me, this is where you get the power of SOA, and the flexibility to
> > exchange messages with parties that weren't there yesterday.
> >
> > I know you all now probably think I'm crazy, but does this make sense?
> >
> > Is it the same or different than what your understanding is?
> >
> > ast
> >
> > [1] http://www.idealliance.org/papers/xml02/dx_xml02/papers/03-02-04/03-
> > 02-04.pdf
> > [2] http://www.semanticcore.org/requirements/InterfaceAdaptation.pdf
> > [3] http://colab.cim3.net/file/work/SICoP/2006-02-
> > 09/Presentations/CCasanave02102006
> > [4] http://www.w3.org/TR/ws-arch/
> > [5] http://www.w3.org/TR/2004/NOTE-ws-gloss-20040211/
> >
> > On Mon, 2006-03-27 at 23:20, Cory Casanave wrote:
> > > Andrew,
> > > One think I suspect we can all agree on is that there are multiple
> > > applications for SOA. Perhaps a little more background on the kinds of
> > > problems we are trying to solve would be appropriate, below is our
> focus.
> > >
> >
> > > Business Need; Collaboration and integration
> > >
> >
> > > The idea of an isolated company, organization, mission or application
> > has
> > > become the exception. It is simply impractical to think of what you or
> > your
> > > organization offers without considering the environment in which it is
> > > offered and performed. Businesses have their supply chains, value
> > chains
> > > and business processes. Defense has joint missions and collaborative
> > > forces. Applications require integration and interoperability.
> > >
> >
> > > In each case the problem is; how to all these things work together? The
> > > problems is also that how it works together is a dynamic environment as
> > > parts and pieces get outsourced, insourced, or modified. The problem is
> > > also that most solutions to enabling these things to work together get
> > tied
> > > to particular processes, information or technologies such that it
> > becomes
> > > brittle and inflexible.
> > >
> >
> > > This is the problem we wish to address - how things work together for a
> > > common purpose while retaining agility. This problem exists at many
> > levels,
> > > from a worldwide scale where there is collaboration between countries
> > and/or
> > > major organizations to how people work together within a department.
> > These
> > > "big" collaborations are realized by smaller and still smaller
> > > collaborations - until you have a small group executing their specific
> > > "business process" on their specific information to realize their part
> > in
> > > the larger picture.
> > >
> >
> > > A community may be small or large, the smallest being a pair of roles
> > > interacting for some purpose, the most common example being a retail
> > > purchase - buyer and seller. But communities are often large, such as
> > the
> > > financial management community of a large enterprise.
> > >
> >
> > > Where people, organizations, missions or countries work together for a
> > > common purpose - there must be some element of agreement, some implicit
> > or
> > > explicit understanding of how they are going to work together for that
> > > purpose. That agreement may be a simple sales agreement to a complex
> > > multi-lateral collaboration of many parties. We express this by saying
> > that
> > > people and organizations are actors playing roles with given
> > > responsibilities within a community and they enact their common purpose
> > by
> > > behaving and interacting according to the contract of that community.
> > > This is the architecture of that community.
> > >
> >
> > > We can also look at this community of actors playing roles as each
> > providing
> > > a service to the community - this is the "larger" view of service, more
> > akin
> > > to a business service - like maintaining a fleet of vehicles. Thus the
> > > architecture of the community is the business view of the "Service
> > Oriented
> > > Architecture".
> > > Note: This kind of business service of an actor playing a role in a
> > > community is related to, but not the same as the service interfaces one
> > > finds in middleware technologies, such as web services.
> > >
> >
> > > Between these actors playing roles there are interactions - these
> > > interactions are frequently bi-directional, asynchronous, choreographed
> > and
> > > long-lived. They represent the "conversations" between the parties
> > playing
> > > the roles. Each of these conversations generally correspond a pair of
> > > service interfaces, one for each side of the conversation. These
> > service
> > > interfaces can be instrumented in technology, and when they are, you
> > have
> > > provided a vehicle for that community to operate more efficiently and
> > > openly. You have provided a way for the "business process" of the
> > community
> > > to happen without any special monitor or control, but as the natural
> > > progression of actors playing their role based on the community process.
> > >
> >
> > > So for us, from the perspective of a "community" the interesting
> > > architecture is how all of these actors work together, and by extension,
> > how
> > > all the services work together for a business purpose. A single
> service,
> > > out of context, can provide value - but an architecture of a community
> > of
> > > roles and services can transform an enterprise or influence a society.
> > >
> >
> > > It is this kind of community we would like to demonstrate - how it can
> > be
> > > described, architected and realized with SOA. The paradigm we use to do
> > > this brings together standards based collaboration modeling (Based on
> > > OMG-EDOC), information modeling (Based on UML) and process modeling into
> > a
> > > cohesive architecture for a community.
> > >
> >
> > > A specific example is an architecture we have just done for the GSA'a
> > CFO
> > > for their Financial Management Line of Business - how can GSA organize
> > to
> > > provide financial management services within GSA and externally. This
> > is
> > > what we would consider an SAO in that it describes these communities,
> > the
> > > roles and interactions, the information models and processes. (You may
> > also
> > > consider that this is more than an SOA in that it also shows how some of
> > the
> > > roles are implemented, but at the top is the SOA). This SOA does not
> > > mention any systems, middleware or technology - it is how the business
> > is
> > > understood as collaborating business services. We then derive (Using
> > MDA),
> > > how middleware services interfaces can help realize and implement these
> > > communities. There are about 60 roles and hundreds of service
> > interfaces in
> > > this architecture (not monolithically, they can be understood in smaller
> > > pieces).
> >
> > >
> >
> > > So, this kind of architecture for a community where the goal is to
> > > understand how roles interact using service interfaces to achieve a
> > common
> > > purpose is a great way to utilize SOA. It allows different actors,
> > > technologies, systems and processes to be used "under the covers" to
> > help
> > > the actors play their role. This kind of community simply does not
> > function
> > > without some agreement of this kind, without a community contract. You
> > > can't do "financial management" one WSDL interface at a time.
> > >
> >
> > > This kind of community architecture can be differentiated from
> > applications
> > > where a single "web service" can supply a unique capability without this
> > > kind of context. These, of course, exist and can provide value - it is
> > > another application of SOA. But the architecture here is focused on the
> > > individual service interface, less so on the environment or community.
> >
> > >
> >
> > > The demo outline we presented is a minimalist and simple community, but
> > > intended to show this community effect based on the business need for
> > > collaboration and integration. You could, of course, come up with any
> > > number of communities to demo. Another kind of demo could be based on
> > other
> > > business needs or approaches to applying MDA - I think some of the other
> > > ideas are more along this line. Our business stakeholders should help
> > guide
> > > us on what kind of problem will resonate with the business community.
> > >
> >
> > > Regards,
> > > Cory Casanave
> > >
> >
> > > > -----Original Message-----
> > > > From: soa-forum-bounces@xxxxxxxxxxxxxx [mailto:soa-forum-
> > > > bounces@xxxxxxxxxxxxxx] On Behalf Of Andrew S. Townley
> > > > Sent: Saturday, March 25, 2006 12:03 PM
> > > > To: Service-Oriented Architecture CoP
> > > > Subject: Re: SOA Semantic Variation ( was RE: [soa-forum] RE: SOA
> > > > CommunityDemoCon Call)
> > > >
> >
> > > >
> >
> > > > Hi folks,
> > > >
> >
> > > > I've combined some of the points from both Cory and Ken into one
> > > > response. Please see in-line.
> > > >
> >
> > > > On Fri, 2006-03-24 at 22:32, Cory Casanave wrote:
> > > > > It is this contract of interaction that is the essence of SOA, this
> > is
> > > > what
> > > > > allows multiple actors to play roles as providers or users of
> > services.
> > > > It
> > > > > is the glue.
> > > >
> >
> > > > Absolutely correct, but so is Ken's point here
> > > >
> >
> > > > On Sat, 2006-03-25 at 05:02, Ken Laskey wrote:
> > > >
> >
> > > > > The essence of SOA is not that we have architected solutions
> > > >
> >
> > > > > but that we have the power to architect the hooks for solution
> > modules
> > > >
> >
> > > > > that deal with areas which make interoperability difficult now. The
> > > >
> >
> > > > > essence of SOA is we can add new services to fill those voids as
> > > >
> >
> > > > > technology and knowledge grows, and we can keep multiple solutions
> > > >
> >
> > > > > around as long as these are useful. The essence of SOA is that we
> > can
> > > >
> >
> > > > > interoperate (to some extent) with people who moments ago we did not
> > > >
> >
> > > > > know existed.
> > > >
> >
> > > > What Ken pointed out is why the S of SOA is so important. The
> > community
> > > > is defined by the services that are provided to it. The interaction
> > > > models of the services themselves define the interaction models of the
> > > > architecture. This is also where you can get explosive complexity if
> > > > things within the architecture aren't managed correctly. So Cory's
> > > > point about the "contract of interaction" is correct, but it exists
> > only
> > > > between a requester and provider.
> > > >
> >
> > > > The architecture defines how these two agents can communicate, with
> > what
> > > > data models and under what constraints, but it cannot do more than
> > > > that. Satisfying those constraints and being able to participate in
> > the
> > > > community require the business relationships that are the glue that
> > Cory
> > > > mentioned.
> > > >
> >
> > > > > How you get to satisfy that contract is another matter. This is
> > almost
> > > > > always a facade on another system or component or service. How you
> > map
> > > > from
> > > > > this "community" specification to your "internal" specification is
> > > > > interesting and important, but it is not important to the community.
> > > > This
> > > > > is your business (So for the demo, this can be a differentiation
> > point
> > > > for
> > > > > the implementers). I think some of the conversation has been how to
> > > > achieve
> > > > > this façade mapping, which is not then NOT something we have to
> > agree on
> > > > but
> > > > > is a great thing to demonstrate.
> > > >
> >
> > > > Actually, if this is in relation to my comments, then this comes from
> > > > the way I expressed it. I was actually not talking about this type of
> > > > mapping at all. This is what we refer to as "behind the service
> > > > boundary", and it is, as you said, only really relevant to the service
> > > > provider and not to the community of requesters. I'll come to more of
> > > > what I meant below.
> > > >
> >
> > > > > The reason we like MDA is it gets us from the business model
> > (providing
> > > > > context and definition for the processes and messages) to the
> > contract
> > > > of
> > > > > interaction (E.G. WS-* and other technologies) with full tracability
> > and
> > > > a
> > > > > lot of automation. Just this is a big win - far beyond the current
> > > > common
> > > > > practice. Having the business model in the picture tackles many of
> > the
> > > > > "what does this tag mean" questions without a full ontology.
> > > >
> >
> > > > True, but doesn't that pretty-much imply point-to-point interactions
> > and
> > > > limited re-use of commonalities through standardized message types?
> > > >
> >
> > > > These standardized message types may be used by multiple business
> > > > processes. This way you can attempt to define the message fragment
> > > > (e.g. a complex element using XML) and state what that message type is
> > > > intended to be. This says what it is in the context of the entire SOA
> > > > community. Once you have this done, the service model for each
> > service
> > > > specifies the context for how it is actually interpreted by that
> > > > service.
> > > >
> >
> > > > The best example of this sort of thing is an address. You can specify
> > > > the structure of an address and how the elements should be populated
> > (by
> > > > profiling, rolling your own, or pulling in xAL), but that in one case
> > > > the address data returned from the yellow pages is for a business and
> > in
> > > > another case the one returned from the white pages is for a residence
> > is
> > > > dependent on the service creating the message. It may be represented
> > by
> > > > the content model as type="business", but ultimately, the context is
> > > > provided by the service model and the business process it represents.
> > > >
> >
> > > > >From what I've seen of MDA from Cory's XML'02 paper "Enterprise
> > > > Distributed Object Computing" and his referenced presentation, it
> > > > doesn't really look like MDA can handle this very well. MDA seems to
> > > > provide higher levels of abstractions to support more generalized
> > > > process modelling, but it's still dealing with an object-oriented
> > > > approach once you get down to the information model. Once this
> > happens,
> > > > you've defined a representation of the concept and you start getting
> > > > into trouble.
> > > >
> >
> > > > I am not convinced that SOA is about objects. Yes, you need a way to
> > > > ship data around, but the power of shared concepts does not come from
> > a
> > > > particular representation. It comes from a shared understanding of
> > the
> > > > concept. If you have this, why not have a shared representation as
> > > > well?
> > > >
> >
> > > > > So the specification we described in the straw man is only the
> > community
> > > > > contract, with full expectation that interesting approaches will be
> > used
> > > > to
> > > > > adapt this community contract to systems and other SOA models. But
> > the
> > > > > community contract would be our anchor point. The important point
> > here
> > > > is
> > > > > that "SOA", as an "architected" solution (the A in SOA) does not
> > need or
> > > > > expect semantic variation in the contract. But realizing SOA
> > contracts
> > > > will
> > > > > be much easier if semantic approaches are available.
> > > >
> >
> > > > The other thing is: once you have a community, you must have some
> > sort
> > > > of governance of that community (even if it's 'none'). This
> > governance
> > > > model decides how and when shared data models can change. It isn't
> > > > about semantic adaptation at the service boundary, it's about changing
> > > > or extending a data model used by many services in the community. You
> > > > can't cause everyone to change their agent implementations because
> > > > someone has a legitimate need for including more information into a
> > > > common model. I believe that this issue is what both Ken and I were
> > > > trying to highlight (Ken, please feel free to correct me if I'm wrong
> > > > here).
> > > >
> >
> > > > What worries me about what I've seen and read thus far about semantic
> > > > negotiation across ontologies is that this is really trying to provide
> > a
> > > > technical solution to a community problem. It goes back to the
> > > > governance thing I mentioned above. If you have a community, you must
> > > > have some shared understandings within that community. Yes, there
> > will
> > > > always be intersections and touchpoints between communities, but this
> > > > can be resolved by putting the semantic negotiation at those
> > > > intersection points.
> > > >
> >
> > > > The fact that within a single community you can have a nearly infinite
> > > > variation in the way the data for an operation is structured and what
> > > > the operation to use it is called is *not* a good thing. Sure they're
> > > > all "semantically equivalent" because what they are supposed to do is
> > > > the same, but how you invoke it should be agreed within the community.
> > > >
> >
> > > > Just because I can define them all in WSDL and figure out how to map
> > > > them does not make it legitimate.
> > > >
> >
> > > > Within a community, there has to be some level of shared sense of
> > > > legitimacy or there is no community. We can't drive on whichever side
> > > > of the road we want to just because we have a car. The community says
> > > > that you drive on the right, so you drive on the right, If you could
> > > > drive from New York to London, you'd need to make some slight
> > > > modifications when you cross the community boundary, but once you're
> > in
> > > > the UK, you drive on the left. If you don't agree, e.g. establish
> > > > legitimacy, there is chaos because everyone's trying to do their own
> > > > thing.
> > > >
> >
> > > > In an SOA, there isn't one contract, there are many contracts; each
> > one
> > > > defined by the service provider's interaction with a requestor. What
> > > > tools you use to hook those two together is not a problem for the SOA.
> > > >
> >
> > > > The SOA says that you can do it and provides the structure to make it
> > > > happen. The architecture is relatively straightforward; the services
> > > > are the hard part.
> > > >
> >
> > > > ast
> > > > --
> > > >
> >
> > > > Join me in Dubrovnik, Croatia on May 8-10th when I will be speaking at
> > > > InfoSeCon 2006. For more information, see www.infosecon.org.
> > > >
> >
> > > >
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