The Nut and Bolts of Use Case Writing: Best Practices and Common Mistakes

III. Techniques for Writing Effective Use Cases

A. Identifying Actors and Goals

The first step in writing effective use cases is to identify the actors and goals that are relevant to the system. An actor is anyone who interacts with the system to achieve a particular goal or objective. Goals describe what the actor wants to achieve by interacting with the system.

To identify the actors and goals, it can be helpful to ask questions such as:

• Who are the primary users of the system?
• What tasks do they need to perform using the system?
• What are the primary goals and objectives of each user?

Once the actors and goals have been identified, they can be used to define the scope of the use cases and ensure that they accurately reflect the needs of the users.

B. Writing Clear and Concise Use Case Names

The names of use cases should be clear and concise, and should accurately reflect the goal that the actor is trying to achieve. Use case names should typically follow a “verb-noun” format, where the verb describes the action that the actor is taking, and the noun describes the object or system that the action is being taken on.

For example, a use case for a user who wants to search for a product on an e-commerce website might be called “Search for Product”.

C. Using Scenarios and Flow of Events

Once the actors and goals have been identified, the next step is to define the scenarios and flow of events for each use case. A scenario describes a particular situation or context in which the use case might occur, and the flow of events describes the steps or actions that the actor takes to achieve the goal.

To create effective scenarios and flow of events, it can be helpful to:

• Use plain language and avoid technical jargon
• Write the scenarios and flow of events from the perspective of the user
• Break the flow of events into smaller, more manageable steps
• Include any preconditions or assumptions that are necessary for the use case to be successful
• Identify any alternative or exceptional flows that might occur

D. Writing Effective Use Case Descriptions

The descriptions of use cases should be clear and concise, and should accurately describe the behavior and functionality of the system from the perspective of the user. Use case descriptions should typically include:

• A summary of the use case, including the actor and goal
• A description of the scenario and flow of events
• Any preconditions or assumptions that are necessary for the use case to be successful
• Any alternative or exceptional flows that might occur
• Any business rules or constraints that apply to the use case
• Any non-functional requirements that are relevant to the use case

E. Specifying Preconditions and Postconditions

Preconditions are the conditions that must be met before the use case can be executed, while postconditions describe the state of the system after the use case has been completed. Specifying preconditions and postconditions can help to ensure that the use case is clearly defined and that any necessary setup or cleanup is included.

F. Including Alternate and Exceptional Flows

In addition to the main flow of events, it’s important to identify any alternate or exceptional flows that might occur during the use case. Alternate flows describe situations where the user takes a different path to achieve the same goal, while exceptional flows describe situations where the use case cannot be completed successfully.

Identifying alternate and exceptional flows can help to ensure that the use case is comprehensive and that all possible scenarios are accounted for.

G. Identifying Business Rules

Business rules are the constraints and guidelines that govern the behavior of a system. They are typically based on organizational policies, legal requirements, or other external factors.