![]() ![]() Multiple interaction fragments are combined to create a variety of combined fragments, which are then used to model interactions that include parallelism, conditional branches, optional interactions. Most of these improvements are based on the idea of interaction fragments which represent smaller pieces of an enclosing interaction. UML 2 has introduced significant improvements to the capabilities of sequence diagrams. It should be the result of a message, either from the object itself, or another.Ī message sent from outside the diagram can be represented by a message originating from a filled-in circle (found message in UML) or from a border of the sequence diagram (gate in UML). You should know how to read and draw the 3 most common diagrams: Class Diagram Sequence Diagram State Machine Diagram The ‘Activity Diagram’ is equally popular as Sequence Diagram, but the Sequence Diagram has clearer notation and is easier to read, so we will use that. Use a sequence diagram to show the actors or objects participating in an interaction and the events they generate arranged in a time sequence. When an object is destroyed (removed from memory), an X is drawn on top of the lifeline, and the dashed line ceases to be drawn below it (this is not the case in the first example though). In UML 2.2 there are 14 types of diagrams. Objects calling methods on themselves use messages and add new activation boxes on top of any others to indicate a further level of processing. Activation boxes, or method-call boxes, are opaque rectangles drawn on top of lifelines to represent that processes are being performed in response to the message (ExecutionSpecifications in UML). If a caller sends an asynchronous message, it can continue processing and doesn’t have to wait for a response.Īsynchronous calls are present in multithreaded applications and in message-oriented middleware. If a caller sends a synchronous message, it must wait until the message is done, such as invoking a subroutine. Solid arrow heads represent synchronous calls, open arrow heads represent asynchronous messages, and dashed lines represent reply messages. Messages, written with horizontal arrows with the message name written above them, display interaction. Note that leaving the instance name blank can represent anonymous and unnamed instances. If the lifeline is that of an object, it demonstrates a role. This allows the specification of simple runtime scenarios in a graphical manner. Sequence diagrams are sometimes called event diagrams, event scenarios.Ī sequence diagram shows, as parallel vertical lines (lifelines), different processes or objects that live simultaneously, and, as horizontal arrows, the messages exchanged between them, in the order in which they occur. Sequence diagrams are typically associated with use case realizations in the Logical View of the system under development. It depicts the objects and classes involved in the scenario and the sequence of messages exchanged between the objects needed to carry out the functionality of the scenario. A sequence diagram shows object interactions arranged in time sequence. It is a construct of a Message Sequence Chart. A sequence diagram is an interaction diagram that shows how processes operate with one another and in what order.
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