MoSCoW method

Background

This prioritization method was developed by Dai Clegg and first used extensively with the agile project delivery framework Dynamic Systems Development Method (DSDM).

MoSCoW is often used with timeboxing, where a deadline is fixed so that the focus must be on the most important requirements, and as such is a technique commonly used in agile software development approaches such as Scrum, rapid application development (RAD) and DSDM.

Prioritization of MoSCoW requirements

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

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 delivery timebox. 'Won't have' requirements are either dropped or reconsidered for inclusion in later timeboxes. (Note: occasionally the term Would like is substituted for Won't have, to give a clearer understanding of this choice).

Use of MoSCoW in new product development

In new product development, particularly those following agile software development approaches, there is always more to do than there is time or funding to permit (hence the need for prioritization).

For example, should a team have too many potential epics (i.e., high-level stories) for the next release of their product, they could use the MoSCoW method to select which epics are Must have, which Should have, and so on; the minimum viable product (or MVP) would be all those epics marked as Must have. Oftentimes, a team will find that, even after identifying their MVP, they have too much work for their expected capacity. In such cases, the team could then use the MoSCoW method to select which features (or stories, if that is the subset of epics in their organisation) are Must have, Should have, and so on; the minimum marketable features (or MMF) would be all those marked as Must have. If there is sufficient capacity after selecting the MVP or MMF, the team could then plan to include Should have and even Could have items too.

Criticism

Criticism of the MoSCoW method includes:

Lack of rationale around how to rank competing requirements: why something is must rather than should.

Ambiguity over timing, especially on the Won't have category: whether it is not in this release or not ever.

Potential for political focus on building new features over technical improvements (such as refactoring).