Even simple Use Case Diagrams should be documented

Mistake #1 – No Use Case Diagram

You should always include a Use Case diagram regardless of how simple it is.   There are two main reasons for this:

1. Provides a sense of scope to the reader

First, it gives a clear picture to the reader showing the scope of the documentation following.  For example – if the ready sees a single actor and single use case in the diagram, they can expect a rather short document, unlike a diagram with 3 actors and 8 use cases which would indicate a rather lengthy document.

2. Simple Use Case diagrams can be combined into a Use Case Model

Second, by providing a diagram in every Use Case document, it makes it much easier for an architect or Senior Business Analyst to reconstruct the system by piecing together all the diagrams into a viable Use Case Model.  This becomes more important if you are developing a large system with a lot of decomposition at various levels of abstraction.  This also becomes important if you are trying to make changes to and existing system that does not already have a Use Case Model.   By injecting these diagrams into documentation, a full or nearly complete model can be constructed over time.

Post your thoughts:  Do you always document the Use Case Diagram?

Tagged as: Business Analyst, Requirements, UML, Use Case Documentation