Objec oriented Analysis and design Pattern
- 1. ARCHITECTURAL MODELING OBJECT ORIENTED ANALYSIS AND DESIGN PATTERNS ASHISH KUMAR THAKUR 16951A0522
- 3. Events 1. An event is the specification of a significant occurrence that has a location in time and space 2. Anything that happens is modeled as an event in UML 3. In the context of state machines, an event is an occurrence of a stimulus that can trigger a state transition 4. Four kinds of events :– -> signals, calls, the passing of time, and a change in state. 5. Events may be external or internal and asynchronous or synchronous
- 6. Signal Event A signal event represents a named object that is dispatched (thrown) asynchronously by one object and then received (caught) by another. Exceptions are an example of internal signal 1. Signal events may have instances, generalization relationships, attributes and operations. Attributes of a signal serve as its parameters
- 7. Signal Event A signal event may be sent as the action of a state transition in a state machine or the sending of a message in an interaction A signal event is an asynchronous event
- 8. SIGNAL EVENt
- 9. Call Event 1. A call event represents the dispatch of an operation. 2. A call event is a synchronous event
- 10. Time and Change Events 1. A time event is an event that represents the passage of time 2. Modeled by using the keyword ‘after’ followed by some expression that evaluates to a period of time which can be simple or complex 3. A change event is an event that represents a change in state or the satisfaction of some condition 4. Modeled by using the keyword ‘when’ followed by some Boolean expression
- 11. Time and Change Events
- 12. Sending and Receiving Events 1. For synchronous events (Sending or Receiving) like call event, the sender and the receiver are in a rendezvous (the sender dispatches the signal and wait for a response from the receiver) for the duration of the operation. When an object calls an operation, the sender dispatches the operation and then waits for the receiver 2. For asynchronous events (Sending or Receiving) like signal event, the sender and receiver do not rendezvous ie,the sender dispatches the signal but does not wait for a response from the receiver. When an object sends a signal, the sender dispatches the signal and then continues along its flow of control, not waiting for any return from the receiver
- 13. Signals and Active Classes
- 14. Signals
- 15. SIGNALS 1. Signals are model elements that are independent of the classifiers that handle them. Signals specify one-way, asynchronous communications between active objects. 2. Signals are often used in event-driven systems and distributed computing environments
- 16. State Machine
- 17. State machine 1. A state machine is a behavior that specifies the sequences of states an object goes through during its lifetime in response to events. 2. Graphically, a state is rendered as a rectangle with rounded corners. A transition is rendered as a solid directed line 3. State machines are used to specify the behavior of objects that must respond to asynchronous stimulus or whose current behavior depends on their past
- 18. States A state is a condition or situation during the life of an object during which it satisfies some condition, performs some activity, or waits for some event.
- 20. Processes and Threads 1. A process is a heavyweight flow that can execute concurrently with other processes. 2. A thread is a lightweight flow that can execute concurrently with other threads within the same process 3. An active object is an object that owns a process or thread and can initiate control activity. 4. An active class is a class whose instances are active objects
- 21. Time and Space