Collaboration and State Modeling

Shows how critical objects collaborate within a use case. Collaboration diagrams are similar to sequence diagrams. Collaboration diagrams focus on key transactions. Sequence diagrams follow the flow of entire use cases (emphasis on time ordering). Collaboration diagrams add extra detail related to timing of messages. Captures the lifecycle of one or more objects.


Expressed in terms of: Different states objects can assume Events that cause changes in state Basic elements: Initial state - hollow circle containing a black dot. Each additional state - rectangle with rounded corners. Three standard events: Entry Exit Do Transition - an arrow between two states. How many state diagrams are needed?


Every object has a state machine. Object is created. Sends messages. Receives messages. It is destroyed. In reality, most state machines are boring, so don't waste time drawing them. Don't diagram an object with two states, on and off. Readability is important. Remarkably similar to flowcharts. Swim lanes - group a set of activities according to who is performing them. A good way to understand/model business processes.