UML

1.Use case diagrams

•  Determining the user requirements. New use cases often generate new requirements.
• Communicating with clients. The simplicity of the diagram makes use case diagrams a good way for designers and developers to communicate with clients.
• Generating test cases. Each scenario for the use case may suggest a suite of test cases.

2. Class diagrams:

• Class diagrams are the backbone of Object Oriented methods. So they are used frequently.
• Class diagrams can have a conceptual perspective and an implementation perspective.During the analysis draw the conceptual model and during implementation draw the implementation model.

3. Interaction diagrams (Sequence and/or Collaboration diagrams):

• When you want to look at behavior of several objects within a single use case. If you want to look at a single object across multiple use cases then use statechart diagram as described below.

4. State chart diagrams:

• Statechart diagrams are good at describing the behavior of an object across several use cases. But they are not good at describing the interaction or collaboration between many objects. Use interaction and/or activity diagrams in conjunction with the statechart diagram to communicate complex operations involving multi-threaded programs etc.
•  Use it only for classes that have complex state changes and behavior. For example: the User Interface (UI) control objects, Objects shared by multi-threaded programs etc.

5. Activity diagram:

• Activity and Statechart diagrams are generally useful to express complex operations.The great strength of activity diagrams is that they support and encourage parallel behavior. An activity and statechart diagrams are beneficial for workflow modeling with multi- threaded programming.