I think we are more bullish on swapping service implementation, but that's a 
consequence of
1. telling people they have to "design for change". The more you make your 
service a reflection of an implementation, the harder it will be to swap it for 
another. You have to work hard at decoupling the interface from the 
implementation. It isn't a given just because it it uses XML and a Web 
Service...
2. We have a long history of doing the same thing in Component Based 
Development (we are CBDI Forum after all...). Again we saw that replacement not 
reuse was often the goal. Hence we defined CBD standards and guidelines to 
facilitate that - separating interface from implementation
3. we also encourage people to take a facade type approach. Use a facade to act 
as a 'broker' between the service interface and the implementation. No one 
expects that a new implementation will have no impact, but if the 'hard work' 
is done behind the facade, it should still have no impact on the consumer.

Lawrence
(everware-CBDI.com, cbdiforum.com)

--- In [email protected], "Rob Eamon" 
<rea...@...> wrote:
>
> In other words, service interface is separate from service implementation? 
> This is the core SO principle.
> 
> I'm still bearish on the notion that a service implementation can be swapped 
> out for another with zero consumer impact. I've never seen a meaningful 
> implementation of anything be swapped out without significant effort. Some 
> low-level technical components can and have been swapped out but that's not 
> the level we're addressing here?
> 



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