You may also discover that objects you originally thought should be involved in a particular process shouldn't be involved at all! Modeling Use Cases In addition, sequence diagrams help you easily identify unnecessary messages between objects and factor them out. At a higher level, it also helps you comprehend the overall flow of a particular process. In contrast, when you document your thought process in a sequence diagram, suddenly the answers to these questions become crystal clear. These questions are very difficult to answer correctly when you simply try to envision object messaging in your head. However, once you decide to elevate your programming by using business objects in your applications, sequence diagrams help you answer two very important questions: This is because if you're not using business objects, most of your application logic resides inside methods of user interface objects or in functions and procedures?and there really isn't much messaging that occurs between objects. Why use Sequence Diagrams?Īs mentioned in the previous article on class diagrams, unless you are using business objects in your applications, you won't have much need for sequence diagrams.

While the collaboration diagram's main focus is to show how objects are associated with each other, sequence diagrams show the time ordering of messages between objects. Sequence diagrams are closely related to collaboration diagrams (discussed in the next article in this series). They are most often used in the construction phase of software projects and are especially useful when analyzing the process-intensive portions of your application. This third article in the series covers one of the most interesting diagrams in the UML - the sequence diagram. You often create a sequence diagram to model the logic of a use case. Sequence diagrams can help you comprehend and solve difficult issues in the process-intensive portions of your applications. It helps you document and understand the dynamic aspects of your software system - specifically the sequence of messages that are sent and received between objects. The Sequence Diagram is one of the most interesting and useful diagrams in the Unified Modeling Language (UML).

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