Lecture 8 - Behavioural Modelling 1

Lecture 8 - Behavioural Modelling 1

1. Object-Orientated Design

   • Used to investigate the precise behaviour of the system to complete class descriptions
   • UML provides a number of alternatives for representing the behaviour of systems
   • Examine documentation to produce diagrams
     • Use Cases/Scenarios
     • CRC Cards
     • Class Diagrams

2. State Diagrams

   • Class diagrams provide basic structure for the system
     • But need to model behaviour (i.e. what happens inside each class)
       • Second Class diagram from lecture 6
   • Dynamic Modelling
   • Shows the operation of each class
   • Actions within states indicated by keyword 'DO'
   • Identifies States an object may pass through
     • Together with stimuli that change state fir a given class
   • States belong to a single class and represent combinations of attribute values that may occur
   • An 'Event' is something which triggers a state transition
     • Not necessarily belonging to a class
     • Caused by object receiving a message
     • Certain condition being met
     • Condition is a boolean expression

3. Collaboration Diagram

   • Need to model interactions between objects
   • Shows interactions between object for a given scenario
   • Objects shown as rectangular boxes
   • Messages are noted on association lines between objects with arrows showing the direction of the message
   • Sequence numbers used to record chronology of messages

4. Complete Class Diagrams

   • Collaboration Diagrams show what messages need to be sent
   • Use these to associate operations with the classes
   • Does sender of recipient perform operation?
     • Use rule that state variables should only be accessible within a class/subclass
     • If an action is required in a number of places
       • Place implementation (method) within a single class