Monday, February 02, 2004

Class Ownership #4 - Sequence Diagrams

I started this thread on the FDD website to discuss the problematic nature of class owenrship and the requirement to draw a sequence diagram as part of Step 4 - Design By Feature, whilst using the Together Control Center product in its code-diagram synchronous mode, i.e. the code is the model and the model is the code - there are no model files, just .java files.

First I ask the Feature Team to draw the sequence diagram for a Feature on a white board. I then ask the diagram creator to make the method signatures in all the classes - breaking the class owner constraint for a few brief minutes. I then have the classes checked-in. The diagram creator then draws the diagram with all the method signatures in place. This allows Together to prompt for the method call between classes on the diagram which makes drawing the diagram easier and faster.

In the event that a class in a sequence is currently checked-out by its owner due to work-in-progress, I ask the diagram creator to comment the method arrow on the sequence diagram rather than designate an “operation”. This looks the same on the diagram but makes no changes to the code. This means that the diagram creator did not have to check-out the class but that the code and diagram are not synchronized.

Then the design review occurs. The diagram is checked-in.

In the original FDD project, Together did not keep sequence diagrams and code synchronized so that the act of drawing a sequence diagram did not create a need to lock class files. I would like to hear how others are dealing with this now and what is considered to be best practice.