Defining use cases

Use cases are built to refine a set of requirements based on a role or task. Instead of the traditional list of requirements that may not directly address the use of the solution, use cases group common requirements based on the type of role or goal. Use cases define what the users or roles will be doing in the solution, a business process defines how they will perform those functions.

About this task

A use case represents the list of tasks that actors can perform, and is directly related to the requirements of the business process. Use cases are a recognition of the requirements that the project must achieve. To document a use case, define the purpose requirements, provide an introduction, and list the different actors or roles for a given scenario.

Procedure

  1. Identify and define the actors.
    1. Identify all the key users of the system. The key users are the ones for whom the system is being built.
    2. Identify all the other users of the system, including automated systems and users in support and managerial roles.
    Example of the actors for a use case for introducing a new product: To introduce any new products an electronic store requires someone from a marketing role to write a description of the item, and someone from the photo department to provide if one is not provided by the vendor. Therefore, the list of user roles will include the vendor, the marketing role, and the photographer role, and each will play a part in the use case for introducing a new product. Here, the vendor submits the product for review, the marketing role introduces the new product, and the photographer takes the photo.

    The task that the vendor does is its own use case. The task that the marketing person does is a separate, related, use case. The task that the photographer does is a third, related, use case.

  2. Match the user requirements to a use case and document the role names and descriptions for the role names by using the use case template.

    The purpose of matching requirements to use cases is to provide a basis of communication between the clients and the solution developers. The use cases helps build the structure and provides the information for the business process that the solution developer will use to create a workflow.

    Example of defining requirements: There are three user roles, the vendor, the marketing role, and the photographer. The marketing role is in charge of introducing the product. Users in this role need to write the product information and use the product to ensure that they understand what the product does. The marketing person is dependent upon the other user roles. The photographer is in charge of taking pictures of the product for hardcopy or softcopy. The vendor in is charge or submitting the product for review.