What is DSDM (Dynamic Systems Development Method)?
DSDM is one of agile's elders (1994), distinctive for wrapping iterative delivery in full project governance: fixed time, fixed cost, fixed quality — scope alone flexes, enforced through MoSCoW prioritization where Must-haves are guaranteed and Coulds are the contingency. Its philosophy: never compromise the deadline; compromise the wish list.
Its other trademark is breadth: unlike team-level frameworks, DSDM covers the whole project life cycle — feasibility, foundations, delivery, deployment — which is why it survives in contract-heavy and corporate settings.
Worked example
A government portal must launch on the date the legislation names — no flex. DSDM frames it: budget fixed, date fixed, Musts (apply, pay, receive certificate) guaranteed; Shoulds (saved drafts) probable; Coulds (dashboard) explicitly the buffer. Development hits turbulence, the Coulds evaporate, two Shoulds slip to release two — and the legal deadline passes with the system live. Scope bent so the promise didn't.