Summary

Use a use case diagram as the first step to functional requirement capture. A use case diagram consists of actors and use cases. An actor is a classification of agents external to the information system that interact with the system. A use case is a function of the information that must be participated by at least one actor. A use case must be complete and provide value to at least one actor.

The most important point to remember is that we are trying to capture the functional requirements, but not how things are done in details. Focus on ``what'' and not ``how'' for now.