Just ran across, quite by accident, a blog post from last spring from Johan den Haan on the "Architectural requirements for Service Oriented Business Applications." This is a clear, consistent, well described web post on SOA and service architecture. I recommend it highly.
About the Author: Nick Malik
President of Vanguard EA, an Enterprise Architecture consulting firm in Seattle focused on the Pacific coast of the US. Nick has over 30 years of professional experience in management, systems, and technology. He is the co-author of the influential paper "Perspectives on Enterprise Architecture" with Dr. Brian Cameron that effectively defined modern Enterprise Architecture practices, and he is frequent speaker at public gatherings on Enterprise Architecture and related topics. He coauthored a book on Visual Storytelling with Martin Sykes and Mark West titled "Stories That Move Mountains".