System analysis and design Safaa s.y. dalloul

Use Cases

Unit 5: Use cases Building Use Case Introduction Elements of use case Basic Information Inputs and Outputs Details Building Use Case Identify the major use cases Identify the major steps within each use case Identify elements within steps Confirm the use case Cycle through the above steps iteratively

Introduction A use case is a formal way of presenting how a business system interacts with its environment. A use case depicts a set of activities performed to produce some output result. Each use case describes how an external user triggers an event to which the system must respond.

Why do you think we need to draw the use cases? Introduction Why do you think we need to draw the use cases?

Introduction To help us better understand the situation and help make the following design step simpler. It is also important to create use cases when we are reengineering processes. When creating use cases, the project team must work closely with the users to gather the information needed.

Determine the elements of Use Case

Elements of use case A use case contains fairly complete description of all the activities that occur in a response to a trigger event. While there are numerous pieces of information in the use case, the information is organized into three main parts: basic information, inputs and outputs, and details.

Basic Information Inputs Outputs Details

Elements of use case Basic Information Each use case has a name and number, the number is simply a sequential number that serves to reference each use case. The importance level maybe assigned to indicate the relative significance of the use case in the overall system.

Elements of use case Basic Information The primary actor refers to the external user that triggers the event to which the system response. Another element of basic information is the trigger for the use case. Use cases are written from the bird's eye view of the system.

Elements of use case Inputs and Outputs Each of the major inputs and outputs to the system case described along with their sources or destination. These are all possible inputs and outputs. Building case is a gradual sharing work for analysts and users.

Elements of use case Details These steps are the activities that are performed during the use case, such as taking patient name and address, check for appointment and so on. These steps are listed in the order in which they are performed and any conditional steps are clearly noted.

Building use cases Process of Developing Use Case Identify the major use cases Identify the major steps within each use case Identify elements within steps Confirm the use case Cycle through the above steps iteratively

Building use cases Process of Developing Use Case Identify the major use cases Activities   Start a use case form for each use case. If more than nine, group into packages

Building use cases Process of Developing Use Case Identify the major use cases Questions   Ask who, what, and where about the tasks and their inputs and outputs What are the major tasks performed? What triggers this task? What tells you to perform this task?

Building use cases Process of Developing Use Case Identify the major use cases Questions   What information/forms/reports do you need to perform this task? Who gives you these information/forms/reports? What information/forms/reports does this produce and where do they go?

Building use cases Process of Developing Use Case Identify the major steps within each use case Activities   For each use case, fill in the major steps needed to process the inputs and produce the outputs

Building use cases Process of Developing Use Case Identify the major steps within each use case Ask how about each use case:   How do you produce this report? How do you change the information on the report? How do you process forms? What tools do you use to do this step (e.g., on paper, by email, by phone)?

Building use cases Process of Developing Use Case Identify elements within steps Activities   For each step, identify its triggers and its inputs and outputs

Building use cases Process of Developing Use Case Identify elements within steps Ask how about each step   How does the person know when to perform this step? What forms/reports/data does this step produce?

Building use cases Process of Developing Use Case Identify elements within steps Ask how about each step   What forms/reports/data does this step need? What happens when this form/report/data is not available?

Building use cases Process of Developing Use Case Confirm the use case Activities   For each use case, validate that it is correct and complete Question Ask the user to execute the process using the written steps in the use case – that is, have the user role-play the use case

Building use cases Process of Developing Use Case Cycle through the above steps iteratively For each use case, perform the previous steps, and maybe you'll need to update one use case depending of new information that could catch.

Role-Play

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