How to properly deal with ER and UML diagram management

Question

When learning about these tools, I (naively) thought that mapping about the business space could be front loaded by doing it only once and refering to those diagrams for each project within a single business unit. However, I am finding that each situation is calling for it's own set of diagrams to properly communicate what's going on. I find that I am dealing with the same objects, but the relationships change.

My first thought to these different situations was that these were sort of disposable* diagrams as they only pertain to a very narrow scope within the business, but I quickly retracted that thought once I found myself scrambling to find the same ER diagram I disposed 3 months ago in a completely different situation. So now I am getting a sence that they are not disposable and should be kept, but I want to avoid just a stack of seemingly contradicting UML and ER diagrams so that someone behind me can make sense of it all. Any suggestions?

Answer 1

An approach that works well is to seperate model content (the objects), and the different views (diagrams). This has worked for me:

1. Create a package for each group of objects or problem domain (e.g. Customers, Products, Finance ...)

2. Create a package for each purpose where you will draw a diagram (e.g. ProductManagementView)

3. Add the objects to the diagram, including all relationships.

If there are view-specific attributes and relationships that you want to capture seperately, create subpackages and use UML's hierarchy/association/dependency constructs to create specific-objects.

E.g. your model may look like this:

 Model
   +- Customer <<package>>
        +- Customer <<entity>>
        +- Address <<entity>>
        +- CustomerService <<package>>
           +- CustomerService <<entity>> -is a-> Customer (+ supportContract attribute)
           +- SupportContract <<entity>>
   +- Product <<package>>
        +- Product <<entity>>
        +- ProductGroup <<entity>>
   +- ProductManagementView
        +- ProductManagementDiagram <<diagram>>
   +- CustomerServiceView
        +- CustomerServiceDiagram <<diagram>>