I think the central idea lies in your clarification after you list your example 
services.  You state that you took a "Business" view of services, as opposed to 
a "IT" view.  Though you don't explicitly state it, I think that a "IT" view 
was taken when discussing the CBA route.  One could easily take a "Business" 
view of components, thus arriving at the same architecture, albeit at a much 
lower level of granularity.

In the end, I think that the superior architectural approach will end up being 
a mixture of both, SOA at a high, corse grained level that wraps a CBA, at a 
more fine grained level.

This is, of course, nothing that new.  A similar architectural approach was 
taken in back in the CORBA days, though the the abstraction was not pushed as 
high as it is today.  It was thought that a coarse CBA could be used to 
encapsulate a fine grained OOA. 

Thoughts?

Griffin
http://blog.griffincaprio.com/blog

On Thursday, November 10, 2005, at 08:58AM, Ashley at Metamaxim <[EMAIL 
PROTECTED]> wrote:

>
        
I was recently involved in a workshop looking at the relationship between 
"service oriented architecture" (SOA) and "component based architecture" (CBA) 
as enterprise architecture approaches.
 
We took, as an example, a hospital and tried developing both SOA and CBA views. 
This is roughly what emerged:
 
1. SOA View
--------------------
In the SOA view the hospital was viewed as a set of services, which could 
potentially be provided by different suppliers. Example services were: 
Hospitality, Catering, Pathology, Theatre, Specialist. (Note that we took a 
"Business" view of services rather than an "IT" view, along the lines suggested 
by Pat Helland of Microsoft). We derived a IT architecture from this, by 
aligning the data and functionality to the services. This led to an 
architecture in which the data/functionality for a given patient was 
distributed to different services: "Hospitality" owning information about 
patient accommodation and nursing routine; "Catering" about dietary 
requirements; "Specialist" owning medical notes; etc.
 
2. CBA View
--------------------
The CBA view (loosely based on the approach recommended in the book "UML 
Components" by Daniels and Cheeseman) drove the architecture from the core 
business entities and built services around them. In this approach, basic 
patient data and functionality was not distributed but owned by a single 
"Patient" component.
 
This example suggests that SOA and CBA lead to different results when applied 
to enterprise IT architectures. I would be interested in any views on the 
following questions:
 
Is this a valid/useful conclusion?
If so, can SOA be regarded as "superior" to CBA as an architectural approach?
 
Any views/comments welcome.
 
Rgds
Ashley





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