Describe the functionality and users (actors) of the system. Depict the behaviour of the system, as it appears to an outside user. Object Oriented Design and Analysis Introduction Use-cases are descriptions of the functionality of a system from a user perspective. Object Oriented Design and Analysis Use Case Diagram 2.
The diagram is used to model the system/subsystem of an application. Use case diagrams consists of actors, use cases and their relationships. 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.These internal and external agents are known as actors. In UML, there are five diagrams available to model the dynamic nature and use case diagram is one of them.
When the requirements of a system are analyzed, the functionalities are captured in use cases.We can say that use cases are nothing but the system functionalities written in an organized manner. Hence, when a system is analyzed to gather its functionalities, use cases are prepared and actors are identified.When the initial task is complete, use case diagrams are modelled to present the outside view.In brief, the purposes of use case diagrams can be said to be as follows −Used to gather the requirements of a system.Identify the external and internal factors influencing the system.Show the interaction among the requirements are actors.Use case diagrams are considered for high level requirement analysis of a system. These requirements are mostly design requirements. We will look into some specific purpose, which will distinguish it from other four diagrams.Use case diagrams are used to gather the requirements of a system including internal andExternal influences. However, this definition is too generic to describe the purpose, as other four diagrams (activity, sequence, collaboration, and Statechart) also have the same purpose. Purpose of Use Case DiagramsThe purpose of use case diagram is to capture the dynamic aspect of a system.
AfterIdentifying the above items, we have to use the following guidelines to draw an efficient use case diagramThe name of a use case is very important. When we are planning to draw a use case diagram, we should have the following items identified.Functionalities to be represented as use caseRelationships among the use cases and actors.Use case diagrams are drawn to capture the functional requirements of a system. Actors can be defined as something that interacts with the system.Actors can be a human user, some internal applications, or may be some external applications.
Another important point is to identify the system boundary, which is shown in the picture. Hence, they have extended relationship. Hence, if we look into the diagram then we will find three use cases (Order,SpecialOrder, and NormalOrder) and one actor which is the customer.The SpecialOrder and NormalOrder use cases are extended from Order use case.
A well-structured use case also describes the pre-condition, post condition, and exceptions. This high level design is refined again and again to get a complete and practical picture of the system. Use case diagram can be imagined as a black box where only the input, output, and the function of the black box is known.These diagrams are used at a very high level of design. But use case diagram never describes how they are implemented.
Use case diagram is used differently to make it suitable for reverse engineering.In forward engineering, use case diagrams are used to make test cases and in reverse engineering use cases are used to prepare the requirement details from the existing application.Requirement analysis and high level design. The same is true for reverse engineering.
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