What is a use-case? How to identify a use-case?

Question

The question is quite generic. What are the points that should be kept in mind to identify a valid use case? How to approach a use case?

Answer 1

A use case identifies, with specificity, a task or goal that users will be able to accomplish using a program. It should be written in terms that users can understand.

Wikipedia's description is overly formal. I'll dig through my other texts shortly. In contrast, the original wiki's article is much more accessible.

An early article by Alastair Cockburn, cited positively by The Pragmatic Programmer, contains a good template.

This question, from just a few days ago, is very closely related, but slightly more specific.

Answer 2

A valid use case could describe:

• intended audience / user
• pre-requisites (ie must have logged in, etc)
• expected outcome(s)
• possible points of failure
• workflow of user

Answer 3

The definition of use case is simple:

An actor's interactions with a system to create something of business value.

More formally:

a sequence of transactions performed by a system that yield a measurable set of values for a particular actor.

They're intended to be very simple: Actor, Interaction, Value. You can add some details, but not too many.

Using use cases is easy. Read this: http://www.gatherspace.com/static/use%5Fcase%5Fexample.html

The biggest mistake is overlooking the interaction between actor and system. A use case is not a place to write down long, detailed, technical algorithm designs. A use case is where an actor does something.

People interact with systems so they can take actions (place orders, approve billing, reject an insurance claim, etc.) To take an action, they first make a decision. To make a decision, they need information

• Information
• Decision
• Action

These are the ingredients in the "Interaction" portion of a use case.