Recommendations on how to decouple services (RSS, REST API) from my UI (webforms) when they share a common model?

I have a web application that is arranged into data, business and UI projects. As the system evolves changes are deployed by building all three projects and deploying them in one package. This has work开发者_StackOverflow中文版ed well and has allowed the illusion of “three tiers” without tackling the communications, versioning issues of truly separate systems.

So along comes a request for XML summaries of some of the data and my thoughts turn to a fancy WCF service that, one day, could be my “Web API” (ahh… the mind.. what a evil little monkey it is). So, assuming this survives the “is that really the best idea?” test here is my question:

What structure have you had the most success with when posed with two evolving “clients” serving content from a single evolving “model”?

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James, your question is rather board as there are a large number of variables that go into choosing the right type of architecture for your needs. I would recommend reading the patterns & practices Application Architecture Guide 2.0 to better understand the options and pick the best one that suits your individual needs.