When Is Something Really SOA?
Here is a question has been on my mind for quite some time - I have some strong viewpoints on it, but would like to hear other viewpoints.
The general question is: When is something really a service-oriented architecture (SOA)?
By this I do not mean "what is an SOA", "what characteristics does an SOA have", etc. Rather, there seems to be a range of points on a continuum (call it the "service continuum", perhaps) at which someone may declare that they have implemented a service-oriented architecture.
In the past, I have pondered the following more specific question (please note that this is all scoped to Web Services-based SOA for ease of explanation):
If I have 2 Web Services that communicate, do I have an SOA?
We can say "certainly not!". One can do point-to-point integration with Web Services just as easily (to a certain degree) as without, with redundant Web Services rather than shared Web Services (a violation of one of the foundational tenets of SOA, which is shared services).
Now let's add some more characteristics:
- The 2 Web Services share another Web Service in common for their processing (i.e. we now have a "shared services" scenario)
- The service provider one or more policies for a service consumer that interacts with it (these policies may address security, QoS, etc.)
- There is an electronic contract for interaction with the service provider (e.g. WSDL)
Add to this the fact that many (correctly, IMO) consider SOA to be a form of Enterprise Architecture, which (at least in my mind) implies enterprise-level benefits.
So the more specific question is:
Given the second scenario above (with the various added characteristics) and the fact that many consider SOA to be a form of EA ---
Is this second scenario large-scale enough that it *really* may be considered SOA? IOW, how large-scale does such an implementation need to be to *truly* be considered service-oriented architecture? When does one arrive at that point?
Booz Allen Hamilton
Visit us online@ http://www.boozallen.com
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