Source: Dai Clegg at Oracle; adopted in the Dynamic Systems Development Method (DSDM)
Sort requirements or tasks into Must have, Should have, Could have and Won't have this time. It makes trade-offs explicit when time or resources are fixed.
When to use it
Use it when agreeing scope for a project or deadline with others.
How to apply it
List all the tasks or requirements for the deadline.
Label as Must have only items without which the outcome fails.
Label important but non-critical items as Should have.
Label nice-to-have items as Could have.
Agree which items are Won't have this time and record them.
Deliver Musts first, then work down the list as time allows.
Tip: If most items end up as Must have, the categories have not been applied strictly enough.