The Last Responsible Moment

At the start of a project the team knows least, and an early commitment narrows the field of view before the facts arrive. Holding a decision open lets learning catch up. But every open decision has a deadline that nobody announces: the Poppendiecks define the last responsible moment as "the moment at which failing to make a decision eliminates an important alternative." A contract renews, an API ships and gets callers, another team builds on an assumption, and the alternative is gone. "If commitments are delayed beyond the last responsible moment, then decisions are made by default, which is generally not a good approach to making decisions." They add that some decisions, such as usability design, layering and component packaging, are best made early, and that "A bias toward late commitment must not degenerate into a bias toward no commitment."

Most Responsible Moment: Wirfs-Brock finds she cannot tell when the last responsible moment is, and that aiming for it lulls her into thinking there will always be time to change her mind; she prefers to decide as soon as a decision has a positive impact, which often comes earlier.