Tulu Tanrikorur of New York Life wrote Business Process Management 101: The Basics of BPM and How to Choose the Right Suite over on Intelligent Enterprise. It's a nice summary of various approaches to considering BPM and related software. However, while Tulu considers the role of rules within BPM, I don't think he considers the role of business rules as a way to create decision services and the role of decision services in BPM. As I have said before, you can over-synchronize rules and processes to your disadvantage and you should not consider the use of rules technology in BPM (or BAM or CEP) to be the same as using rules to automate decisions.
BTW Bruce Silver's great article on this topic in Intelligent Enterprise is here: Analysis: Where Rules Management and BPM Meet