All requirements are important, but they are prioritized to deliver the greatest and most immediate business benefits early. Developers will initially try to deliver all the Must have, Should have and Could have requirements but the Should and Could requirements will be the first to be removed if the delivery timescale looks threatened.
The plain English meaning of the prioritization categories has value in getting customers to better understand the impact of setting a priority, compared to alternatives like High, Medium and Low.
The categories are typically understood as:
- Must have Requirements labeled as Must have are critical to the current delivery timebox in order for it to be a success. If even one Must have requirement is not included, the project delivery should be considered a failure (note: requirements can be downgraded from Must have, by agreement with all relevant stakeholders; for example, when new requirements are deemed more important). MUST can also be considered an acronym for the Minimum Usable Subset.
- Should have Requirements labeled as Should have are important but not necessary for delivery in the current delivery timebox. While Should have requirements can be as important as Must have, they are often not as time-critical or there may be another way to satisfy the requirement, so that it can be held back until a future delivery timebox.
- Could have Requirements labeled as Could have are desirable but not necessary, and could improve user experience or customer satisfaction for little development cost. These will typically be included if time and resources permit.
- Won't have (this time) Requirements labeled as Won't have have been agreed by stakeholders as the least-critical, lowest-payback items, or not appropriate at that time. As a result, Won't have requirements are not planned into the schedule for the next delivery timebox. Won't have requirements are either dropped or reconsidered for inclusion in a later timebox. (Note: occasionally the term Would like to have is used; however, that usage is incorrect, as this last priority is clearly stating something is outside the scope of delivery).
Variants: Sometimes W is used to mean Wish (or Would), i.e. still possible but unlikely to be included (and less likely than Could). This is then distinguished from X for Excluded for items which are explicitly not included.
Also find below few other methods used for product prioritisation:
- RICE method
- Cost of delay
- PriX method
- Story mapping