The Stencil Group has an interesting Analysis Memo on The Vision of Service-Oriented Architectures:
"Observant readers may note that this table omits a column that could be called something like "The Web" - information and applications developed for consumption in web browsers. That choice is not intended in any way to dismiss the hugely significant impact the web had on how users access information. But, to our mind, basic web application design represents a transition phase between client/server and service-oriented design. Web applications dramatically expanded the reach and flexibility with which users could access and modify the information locked away in centralized databases. Service-oriented architectures complete that shift by decoupling application logic and data from monolithic implementations."