Functional and non-functional requirements

A functinal requirement describes what a system should do, while a non-functional requirement describes how it should be done.

Functional requirements of a mobile phone:

• Calling
• Texting
• Emailing
• Phtography
• Noise activation
• Notifications

Non-functional requirements of a mobile phone:

• Stable access to a network
• Good battery life
• Robust bandwidth
• Sufficient storage

Contextual requirements These describe relationships or dependencies between sets of objects in a system.

These are objects that need to be displayed together to make sense for a specific workflow, or to meet the goals of a persona. They may include considerations of a physical environment, and the capabilities / skills of a user.