But use case diagram never describes how they are implemented. Use case diagrams specify the events of a system and their flows. Use case diagram is one of them and its specific purpose is to gather system requirements and actors. To understand the dynamics of a system, we need to use different types of diagrams. Actually these specific purposes are different angles of a running system. Now each and every model has some specific purpose to use. Where to Use a Use Case Diagram?ДЄs we have already discussed there are five diagrams in UML to model the dynamic view of a system. The actor Customer lies outside the system as it is an external user of the system. Another important point is to identify the system boundary, which is shown in the picture. The SpecialOrder and NormalOrder use cases are extended from Order use case. SpecialOrder, and NormalOrder) and one actor which is the customer. Hence, if we look into the diagram then we will find three use cases (Order, Use notes whenever required to clarify some important points.ДЇollowing is a sample use case diagram representing the order management system. Show relationships and dependencies clearly in the diagram.Дo not try to include all types of relationships, as the main purpose of the diagram The name should be chosen in such a way so that it can identify the functionalities performed. The name of a use case is very important. Identifying the above items, we have to use the following guidelines to draw an efficient use case diagram Use case diagrams are drawn to capture the functional requirements of a system. Relationships among the use cases and actors. When we are planning to draw a use case diagram, we should have the following items identified.ДЇunctionalities to be represented as use case Actors can be defined as something that interacts with the system.ДЄctors can be a human user, some internal applications, or may be some external applications. The second thing which is relevant to use cases are the actors. We can say that use cases are nothing but the system functionalities written in an organized manner. When the requirements of a system are analyzed, the functionalities are captured in use cases. Use case diagrams are considered for high level requirement analysis of a system. Show the interaction among the requirements are actors. Identify the external and internal factors influencing the system. Used to gather the requirements of a system. In brief, the purposes of use case diagrams can be said to be as follows в€’ When the initial task is complete, use case diagrams are modelled to present the outside view. Hence, when a system is analyzed to gather its functionalities, use cases are prepared and actors are identified. These requirements are mostly design requirements. Use case diagrams are used to gather the requirements of a system including internal andД®xternal influences. We will look into some specific purpose, which will distinguish it from other four diagrams. However, this definition is too generic to describe the purpose, as other four diagrams (activity, sequence, collaboration, and Statechart) also have the same purpose. The purpose of use case diagram is to capture the dynamic aspect of a system. Hence to model the entire system, a number of use case diagrams are used. A single use case diagram captures a particular functionality of a system. The diagram is used to model the system/subsystem of an application. Use case diagrams consists of actors, use cases and their relationships. These internal and external agents are known as actors. Now as we have to discuss that the use case diagram is dynamic in nature, there should be some internal or external factors for making the interaction.

In UML, there are five diagrams available to model the dynamic nature and use case diagram is one of them.

Only static behavior is not sufficient to model a system rather dynamic behavior is more important than static behavior. Dynamic behavior means the behavior of the system when it is running/operating. To model a system, the most important aspect is to capture the dynamic behavior.

Use case diagram staruml