week12-summ.pdf

Sequence Diagrams: Definition and Basic Concepts  Definition: A sequence diagram is an UML diagram that shows interaction between objects arranged in a time sequence manner.  Used in analysis to show interaction between an actor and the system (we do not see the objects there; no specified meth...

Sequence Diagrams: Definition and Basic Concepts  Definition: A sequence diagram is an UML diagram that shows interaction between objects arranged in a time sequence manner.  Used in analysis to show interaction between an actor and the system (we do not see the objects there; no specified method signatures; less useful)  Their usefulness comes in design, where they are used to depict the collaboration between objects and to specify the message signatures;  The basic notation is given in the next slides Design Object Types Entity object (persistent class) ▪ An object which continues to live after the program execution. ▪ An object about which we persistently store data in a database. ▪ An object usually from a domain model. ENTITY OBJECT Design Object Types Interface object (transient class) ▪ Exists only during run-time ▪ Used by an actor to ▪ interface with the system : ▪ Window ▪ Dialogue box ▪ Menu ▪ Web form Application Program Interface (API) used by other systems to interface with our system. INTERFACE OBJECT Design Object Types Control object ▪An object that contains application logic that does not belong to an entity object : ▪ Business rules ▪ Calculations that involve multiple objects ▪ An object that coordinates communication between interface objects and entity objects CONTROL OBJECT Steps in Creating Sequence Diagrams There are four basic steps to perform when drawing sequence diagrams: ▪ If a CASE tool allows, copy the text of the given use case from the use case narrative and paste it to the left margin of the page. ▪ Add actors ▪ Add boundary and entity objects identified in the use case narrative. ▪ Add the use case controller object, which we will called the use case handler. Its purpose is to handle the entire communication between boundary and entity objects. ▪ We might have some other control objects in a sequence diagram, if needed.