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Writing Effective Use Case Scenarios

Instructor: Jagina McIntyre

Jagina has conducted professional training in communications and analytics for 12 plus years, with a a degree from Kent State University in Journalism and Communications.

This lesson contains everything you will need to know to write an outstanding use case scenario that will make your next software implementation go flawlessly and solve the key problems your users face.

Everything You Need to Know to Write a Use Case

Have you ever wondered how to develop the perfect system or process that customers will love? Or maybe you have been involved with getting a new system off the ground only to be met with disappointment when several key features are missing? Well understanding how to write an outstanding use case is right where you need to be.

A use case is a textual document that outlines just how a task will be performed in any system or process. For the end user it is simply how a process or system will respond to a request. Imagine you just purchased a new smartphone and when you press the 'call' button the device opens up a text message dialogue box instead. The expectation for what the 'call' button would do has not been met. A use case should list what a software does, but should not address how it does it.

The process of writing an exceptional use case includes:

  1. actors - people interacting with the process; often called users.
  2. stakeholders - typically not direct users, but have invested interest.
  3. system or basic flow - items or process required to get to the final outcome.
  4. alternate flow - what happens when basic flow is interrupted.
  5. preconditions - use case can only begin if these rules are true.
  6. triggers - an event that kicks the use case into gear.
  7. goal or outcome - what the user desires to happen for successful completion.

Writing a great use case requires the appropriate balance of detail. Too much detail can begin to resemble a system design document. A use case should not be a technical document. Too little detail could cause a critical step to be missed when designing the new process.

Example

A mother transports her toddler to daycare before heading to work on Monday and Tuesday mornings at 8 a.m., when her husband is out of town on business. When her husband is in town, he transports their child at 10 a.m., before he heads to the office. If the child is not going to daycare, one of the parents needs to call the daycare director. In this case, the actors are the mother and the father. The stakeholder is the daycare director. The system required is a vehicle to transport, gasoline to power the vehicle, a car seat for the child, and a traffic route to get from their home to the daycare.

There is an alternate flow when the husband is out of town, causing the mother to complete the drop off. The precondition is that the day must be either Monday or Tuesday for this event to even occur. The event is triggered at the specified time, dependent on the husband's whereabouts. The goal is to get their child to daycare, so that they can both make it to work.

A use case is a textual document that outlines the steps needed to complete a task in a system to reach a user

Use Case Diagrams

A use case diagram is a graphical representation of a use case. It can sometimes be used to to create a solid visual for what a user wants to see. The use case diagram has a very specific design where stick figures are used to represent the user. Oval dialogues are used to indicate the goals, while leader lines are used to indicate the process or system that joins the user to the goal. The actors position name is written below the line. A rectangle or box drawn around the ovals represent the system limitations. Although these diagrams are not a necessary part of the document, they can be helpful when reinforcing points.

In this example of a use case diagram, each parent is responsible for transporting the child to school. However each parent also has other tasks they are responsible for individually.

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