A common scenario that I see is the case where an organization wants to build a new application with the intent of 'finding services' in the implementation of the project. This is common because current I.T. governance favors 'project funding'. This begs the question, what does the process look like for capturing requirements for a silo-oriented application in a service oriented, mashup, process driven world?
First and foremost, we must recognize that we are not in the object oriented world where we captured requirements as if there were only one type of logic. We live in a world of domain specific languages and self describing interfaces. Capturing requirements as if we didn't know that kind of input our downstream partners need is just plain silly (and obsolete).
A simplified view of the new process looks like this:
Today, we leverage our downstream partners (UI, design, architecture) to help drive full and useful requirements. The analyst leverages the UI/Mashup/Composite specialist to create mockups, prototypes and even working user interfaces. The UI's are then presented back to the business users to help validate the requirements. UI's typically are good at conveying a single users role in a larger process but fail to paint the big picture. To bring breadth to the table, the analyst will call on a process and integration specialists to clarify process steps, human workflow and even the flow of information between legacy systems. In most cases, the 'composite services', 'integrations' or 'process logic' calls atomic services. This is where fine grained business rules, calculations and constraints are housed. The anlayst will leverage the skills of a Service Designer to stub out or mock up an interface (WSDL) along with a dummy implementation.
Our goal is to use a combination of rapid prototyping and extreme programming to quickly create releases that can be presented to the business community for feedback. Modern analysis embraces the following key concepts:
1. It acknowledges that some functions will be shared (as services)
2. It embraces various types of logic (presentation, process, data, etc.) and documents those requirements in a manner that makes sense to the people who have to build it
3. It leverages the techniques we've learned in spiral, iterative, RAD and agile methods limit risk and involve the user
Remember - SOA is only a piece of the puzzle.