Published on March 18, 2008

This post was previously on the Pathfinder Software site. Pathfinder Software changed its name to Orthogonal in 2016. Read more.

Projects start off at the 60,000-foot level — the client wants a widget that allows their users to do X, Y & Z — and need to be brought down to a level of detail where coding can begin. Something I use to start this process is a version of the UML Use Case Diagram.

For those of you not familiar with it, a Use Case Diagram describes the needed functionality in a system. Unlike flow diagrams, however, the use case diagram doesn’t represent the order or number of times the functionality needs to be executed and it doesn’t display any subroutines. Instead, it’s a high-level diagram that identifies the primary tasks an actor/persona needs to be able to do.

The beauty of this diagram is that you’ve now captured the overall view of what the system needs to be able to do in order to allow the user to complete all their tasks. With the high-level activities clearly identified, the diagram easily lets you communicate with your client and get their sign off that the needed functionality has been accurately captured. From here, the team can move onto further defining what’s needed to support this functionality: data modeling, user stories, task flows, etc.