Which should be created first ER Diagram OR Class Diagram?

Question

The very first step i created a DFD. Then i moved on to create a Class Diagram. And while doing that i felt that i should create the ER diagram first. As there were many details which could not be captured in a Class diagram. So, my question should i create ERD first OR Class Diagrams ?

your valuable inputs are appreciated guys!!! thanks for reading

Answer 1

When modeling, I tend to think in terms of doing the diagrams in whatever order makes the most sense to me at the time. Sometimes that's the class diagram first, sometimes that's the entity-relationship diagram, sometimes that's even the sequence diagram. The main thing to remember is that you're trying to understand things and write them down so that other people can understand them too; fretting about what is the best way to order your thoughts isn't nearly as helpful as just getting down to it and writing those parts that you do understand.

[EDIT]: FWIW, I also tend to start my modeling on paper or a whiteboard and only switch to using a computer when I'm getting closer to what I understand to be going on. (I guess I just don't like drawing on computers.) The key is that modeling is about understanding, and not (very much) about computers.