object oriented analysis and design

Question

hi guys,

i'm doing a system these days, my first one actually and i'm in trouble doing OOAD, i need some help from you all, i'm familiar with diagrams drawn in UML,but when given a scenario i can't make a link, can't see a flow of them, for example now i'm designing the system, i've done use case diagrams and activity diagrams and now i'm finding it very difficult to decide the classes according to the situation? i can't find a flow between these diagrams, how can i get class diagrams when i'm done with the above mentioned two diagrams? i'm not that much expert in UML either,just familiar with the diagrams? can some one solve the problem? any suggestion of tutorials? how to analyse a system? what is the problem with me??

regards, Rangana

Answer 1

If you feel like that, don't start with UML. Start with the code itself. Moving from requirements to design is always an intuitive leap, which gets much easier with experience (including the experience of making major mistakes, alas!). There are any number of books that can help you progress faster, but nothing beats actual coding experience to drive your design skills. Skip the class diagrams for now, and focus on the code: class diagrams are just a way of abstracting away details in order to communicate the overall shape of your program, sometimes to yourself! If you're unsure of the details, don't attempt to hide from them...

I'd recommend Craig Larman's Applying UML and Patterns as a starting point addressing most of the software design lifecycle, from a fairly practical and integrated perspective. There are plenty of other books out there: check SO for questions on e.g. general programming books and OO books.

Answer 2

I had the same problem in my project. I have created usecases and requirements then immediately started to code. Once the first codding stage was finished I reversed my code into an UML model and merge it with existing diagrams. It works really well in an iterative way with UML and codding at the same time.

More information about this innovative modeling approach is described at:

http://www.forum-omondo.com/documentation_eclipseuml_2008/reverse/reverse/index.html#1.3_Merge_existing_model_with_modified

http://www.forum-omondo.com/documentation_eclipseuml_2008/waterfall_versus_incrementale_modeling_cycle.html

Answer 3

UML without context might really be hard to use or benefit from. If you are starting creating projects and you do not want to just "hack it", it is a good idea to choose a good methodology for your project. Once you find a suitable methodology, follow it and it will give you pointers what needs to be done, for what reason and sometimes even how to get it done. For example if you had chosen Unified Process, which is free methodology based on Rational Unified Process done by authors of that methodology and UML, you would be guided how to use UML diagrams to support your development process. I recommend reading this book for this purpose - http://www.clearviewtraining.com/books/uml-2-and-the-unified-process