Subtitles of the Movie

The four plus one model presents one way to break down the modeling of an entire system into a series of use. Another way is in terms of the static and dynamic characteristics of the system. This movie defines the static and dynamic aspects of the system and shows which UML diagrams best model these aspects. In addition we'll talk about the implementation of a system which is really a subset of the static model. So let's define our terms, static models show the structural characteristics of the system. Dynamic models show the behavioral characteristics of the system. And implementation models which as I've said are a subset of static show the elements required for deployment of the system. We'll look at each these in turn. Static models show the system's structure, so a static model illustrates the overall structure of the system or some part of it. A static model emphasis the parts that make up the system. Use static models to define class names, attributes, method signatures and packages. In UML diagrams it represents static models include class diagrams which you'll see a lot of, object diagrams and also use case diagrams. A dynamic model on the other hand shows the system's behavior. For example, a dynamic model might show how the system behaves in response to external events. Dynamic model let's you identify the objects that your system needs and how those objects work together through methods and messages. And you should use dynamic models to design the logic and the behavior of the system. UML diagrams that represent dynamic models include sequence diagrams and communication diagrams which are both types of interaction diagrams. They also include state diagrams and activity diagrams. Now implementation models as I've said are a specialized kind of static models. And the implementation model shows the different elements the system requires for deployment. It shows the organization of physical software components and other physical resources such as, hardware and connection paths. UML diagrams that represent implementation models include component diagrams and deployment diagrams and often you'll find these classified under static diagrams because again, implementation models are a subset of that kind of diagram. So static verses dynamic, which model is best for which situation? Static diagrams and especially class diagrams give developers detailed information about classes, data types, parameters and namespaces. You'll often find class diagrams referred to as the backbone of you're UML model so these are very important. Dynamic diagrams such as sequence and communication diagrams help you to define objects in your system and how they interact. Don't skimp on the dynamic diagrams, because a lot of people associate UML diagrams with class diagrams there is a danger of overlooking, for example, the interaction diagrams, the sequence and communication diagrams, but these are very important in designing the logic and the behavior of your system. Identifying objects, showing how these objects must interact in various ways. Dynamic diagrams are equally important, an agile modeling practice recommends developing models in parallel, working on static and dynamic models at the same time and this is really the best way to approach modeling of your system.