Use case :: 1 of 2

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What is it?

A use case is a detailed written description of a sequence of events and interactions between a user and a web site, without specifying the user interface. Simpler, plain-English versions are often called scenarios.

Characteristics

Each written use case should capture:

• The actor - who is using the website, system or application?
• The interaction - what does the actor want to do?
• The goal - what is the actor's goal?

Use cases - because of their origin in software engineering - often encounter difficulty in incorporating user interface (UI) concepts.

What's it for?

In software engineering - where the term use case originated - a use case is a technique for capturing the functional requirements of systems (and systems-of-systems).

Each use case typically provides one or more scenarios that convey how the system should interact with the users - called actors - to achieve a specific business goal or function.

Use case actors may be end users, or indeed other systems.

How to create a use case
Generally, you write a use case in an easy-to-understand narrative. This engages members of the design team and encourages them to be actively involved in defining the requirements. The following eight (8) steps are typical:

1. Identify who is going to be using the website, system or application
2. Pick one of those actors
3. Define what that actor wants to do. Each thing the actor does becomes a use case
4. For each use case, decide on the normal course of events when that actor is using the site, system or application
5. Describe the basic course in the description for the use case. Describe it in terms of what the actor does and what the system does in response that the actor should be aware of
6. When the basic course is described, consider alternate courses of events and add those to "extend" the use case
7. Look for commonalities among the use cases. Extract these and note them

Repeat the steps 2 through 7 for all other actors.

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