The dynamic model is used to express and model the behaviour of the system over time. It includes support for activity diagrams, state diagrams, sequence diagrams and extensions including business process modelling. Sequence diagrams are used to display the interaction between users, screens, objects and entities within the system. It
provides a sequential map of message passing between objects over time. Frequently these diagrams are placed under Use Cases in the model to illustrate the use case scenario - how a user will interact with the system and what happens internally to get the work done. Often, the objects are represented using special stereotyped icons, as in the example below. The object labelled Login Screen is shown using the User Interface icon. The object labelled SecurityManager is shown using the Controller
icon. The Object labelled users is shown using the Entity icon. Activity DiagramsActivity diagrams are used to show how different workflows in the system are constructed, how they start and the possibly many decision paths that can be taken from start to finish. They may also illustrate the where parallel processing may occur in the execution of some activities.
 State ChartsState charts are used to detail the transitions or changes of state an object can go through in the system. They show how an object moves from one state to another and the rules that govern that change. State charts typically have a start and end condition.
Process ModelA process model is a UML extension of an activity diagram used to model a business process - this diagram shows what goal the process has, the inputs, outputs, events and information that are involved in the process.
The object model which we have just been discussing is a static model of classes and their relationships. It does not show how the classes call on one another to perform the functions required in the software system. These dynamic aspects of the object model are usually represented in other diagram types of the UML. We will be briefly discuss interaction diagrams. Interaction diagramsInteraction diagrams show how objects interact with one another. Specifically, they show which objects are currently executing, and what methods they are calling on other objects. There are various kinds of interaction diagrams that can be employed in the UML. We will examine one specific type, the sequence diagram. Sequence diagrams show how objects interact with each other over time. In other words, sequence diagrams show the sequence of interactions between objects. Figure 5.9. Sequence diagram notation in the UML The figure above shows a sequence diagram of how books are checked out of a library. Notice how the objects are arranged horizontally along the top of the diagram, and are represented as rectangle boxes, just as classes are. It is important to notice the colon before the class name in these boxes — this colon tells us that the box represents not a class, but an instance of the class. If the instance should be given a specific name, then the name appears before the colon. For example, “artOfWar : Book” represents an object called “artOfWar”, of class “Book”. This is exactly the same as when specifying attributes in classes (see the section called “Attributes” above). It is important to realise that it is because sequence diagrams represent the interactions a software system undergoes over time that it is interested in objects rather than classes. A running software system consists of instances of classes, and not of the classes themselves. Time is represented vertically, with earlier events happening closer to the top. This means that sequence diagrams should be read from top to bottom. Each object also has a vertical life-line that shows us the object's period of existence. Interactions are represented by solid and dotted lines, each of which has an arrow and a label. Solid lines show method calls, and point from the life-line of the object making the call towards the object which will execute the method. The rectangles along the life-line represent the time over which an object is executing a function. Dotted lines represent a return of control from the object executing a method to and object which had originally called it. Note that the method names should be operations belonging to the object to which the arrow is pointing. “Borrower” calls “requestBook”, an operation belonging to an instance of class “Book”. A useful way of using sequence diagrams is to outline difficult use cases as a sequence diagram: this will highlight what objects are required in developing the use case, as well as what actions each object will perform in order to complete the use case. Further, a sequence diagram can then be thought of as showing how the system reacts to events, the events being the input from the actor in the use case. The UML also prompts us to use sequence diagrams in this way: remember that actors in use cases are themselves classes. We can easily use instance of these classes (of these actors) as valid objects in sequence diagrams. SummaryClass modelling is the key modelling technique for object-oriented designers. If you are in a position to say that you understand class modelling, then you can reasonably claim that you understand object-oriented design. Of course, an understanding of other object-oriented techniques (e.g., use case modelling) will also be helpful. Class modelling centres on a small number of philosophical points, which must be understood extremely well. There is not a great deal of factual material to remember, but these key points are crucial. These are the most important issues:
In constructing a class model, the first step must be to obtain a working list of candidate classes. As design progresses, these classes will be refined and some will be deleted. At an even later stage, new classes will be introduced to support more detailed, implementation-related concepts. A class model is refined by finding and specifying associations. Doing this helps to determine whether the initial choice of classes is a sound one, and how to improve it. Ultimately the class model will be transformed into a computer program. Which diagram show the dynamic aspect of the system?Dynamic UML diagrams describe the behavior of systems. A dynamic diagram describes the operations, actions, and changes that occur in a system over time. A static diagram, on the other hand, describes the characteristics of a system or part of a system.
Which of the following show the static structure of data and the operations that act on the data?Use cases show the static structure of data and the operations that act on data.
What is diagram used to depict the dynamic behavior of the objects in a system?Behavior diagrams depict the dynamic behavior of the elements in your system. The various behavior diagrams are as follows: Activity diagrams show the flow of activities within a system.
What describes the structure of a system in terms of objects attributes associations and operations?In software engineering, a class diagram in the Unified Modeling Language (UML) is a type of static structure diagram that describes the structure of a system by showing the system's classes, their attributes, operations (or methods), and the relationships among objects.
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Which of the following represent dynamic models of interactions between objects
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