Question

So no doubt that building a domain model is something that I think happens best when you approach it as as team. Even going so far as to involve someone who is not technical and a member of the ‘business’ in the modeling sessions. So much can get done quickly when you put the right people in a room and hammer out things on a whiteboard. But what about the times that you don’t have that luxury? What about when you have to build a complex domain model alone? I have been doing this for the past month or so and have done the following:

1. Start off by Noun Idendtification, then use Class-Role-Collaborations to analyze relationships
2. Look for analysis patterns that can be used to refine the model, Party, etc..
3. As soon as I have a handle on the basics, I’ll bust out an IDE and start writing XUnit tests to show that the model let’s me do the things that I want

While these techniques have worked well, I’m not sure they are as efficient as a truely collaborative effort. I think it is easy to get carried away with a concept only to realize later that it violates x or y requirement. What techniques have you used when working in isolation to ensure that your object/domain model is on target?

Answer 1

Everyone does it differently, I think, but…

I almost always start with a Class diagram (usually UML-like and on paper), paying special attention to relationships between classes and their arity. Validation at this stage is mostly trying to understand if the high-level semantics of the entities make sense together.

Then start sketching in the key functions, especially those involved in collaborations. Make sure objects in a collaboration can reach each other through the relationships. At this stage I’ll be using a drawing tool (StarUML).

Then come the gedanken experiments. I mentally walk through the trickiest use cases I can think of and see if I can envision a way to address them with the given design. This isn’t psuedocode, just stepping through each of the major tasks/functions and following the lines of the diagram to make sure I’m not missing callbacks, circular dependencies, etc.

I think one key is to not get too married to any particular aspect of the design until you’ve satisfied yourself that it will probably work reasonably well. In my mind, if you can’t step through a design mentally to evaluate/validate it you either lack some understanding of the problem, or the design on paper isn’t complete enough…

Then, time permitting, set that one aside and see if you can come up with something really different…