A Use Case describes the interaction between a user and the system. The user is termed as “Actor”. The functionality or interaction scenario is the Use Case. The Actor may be a human or an external hardware / software system. The user may assume different roles while interacting with the system to achieve different goals. In order to identify the various Use Cases in the system, you need to find out the functionalities available in the system, user roles, user goals and primary and secondary tasks that the user performs through the system. The title of the use case explains what the user is trying to achieve through the system. (By the term “system” we mean here, a computerized or automated system).
Components of a use case
- Goal or functionality
- Main Scenario (steps for the user to perform the operation on the system), its criteria and outcome
- Alternate Scenario(s) (alternate steps to be followed based on conditions) its criteria and outcome
- Triggers (if any)
- Exception and Error handling scenario
A Business Case describes the interaction between an outside Actor (customer / vendor) and an organization. The “functionality” is a business process. The scenario is a business work flow. Plotting a Business Case helps the business management to determine whether the project will be of value and compares the project with alternate proposals. It also outlines the acceptance criteria for a project.
Use Case versus Business Case
The difference between a Use Case and a Business Case lies in the scope. The scope of a Business Case is an enterprise. The scope of a Use Case is a computer system. Use Cases focus on the functions to be implemented in the system. For a Business Case, the focus is on the services provided by the organization. Use Cases form a part of the functional specification. Business Cases form a part of the requirement specification and are useful for tracking during User Acceptance Testing.
For example, a shopping cart application would be a candidate for a Use Case. The Actor is the buyer. The action is performed on the web application. The goal is to buy an item. The Use Case ends with the user completing the “Buy” action on the web site, since the Use Case only defines the interaction with the system. An example of Business Use Case would be a person ordering groceries at a store. The action is performed on the grocery store (business). The business case ends only when the items are finally delivered to the user, since the Business Case defines the interaction with a business / organization / enterprise.
Both Use Cases and Business Cases capture the processes performed by an actor to achieve a goal. They are both useful to define the interaction based requirements. The scenario described in a Business Case may encompass a few Use Cases (automated actions or steps that involve interaction with a system). There may be situations when a Business Case becomes equivalent to the Use Case. An example is “Flight Check-in On-line”. Check-in is a service provided by the airline business and hence it would be a business case. The entire function is performed by interacting with a software system and hence it can be considered as a Use Case too.
Business Case Templates, and Use Case Templates are often used to promote consistency and professionalism within an organization.