Milestone
A marker of zero duration that a body steers by — a point, not a piece of work.
A milestone says that something is so: the first hundred and forty-four Cells stand; the book is in hand; the crossing is made. It has no length. The activities that feed it have durations, owners and handoffs; the milestone names the threshold they cross, and every activity serves at least one milestone above it. It carries a trigger that is structural — a count, a condition, a recognition, never a calendar day — and two dates: the plan date, which the schedule is computed to with zero Float on the Critical Path, and the marker, standing one season later. The season between is contingency, shown on the wall as it is consumed.
It is load-bearing because it is what Pull planning pulls from and what every finish-by is inherited from. Without milestones a plan has no top and no way to be wrong; with them, lateness becomes visible early enough to be answered. And it is what lets levels weave: each level publishes its milestones, the level above plans over them, and The plan of the whole comes back down as the upper half of every card.
Three things keep it honest. The milestone serves the work: when it is missed it has done its job, and the response is to re-pull and recover within the next one or two, or to move the end openly, by Proposal, with its why. A milestone is not the window — milestones are set by us and can be reset; a window is set by reality. And temporal markers, the solstices and equinoxes the seasons turn on, are never milestones.
Also called: The Milestones · the plan date Stands on: Pull planning · The activity table · The Intent Opens onto: Float · Critical Path · Honesty about time · Measure everything, manage to the milestones · Temporal markers apart from milestones In play: table · Home · beyond Sources: Milestone (wiki term page, drafts, unreviewed; the fullest treatment) · Milestones (wiki root page) · The LIØNSBERG Operating System (book, draft v0) §5 · The LIØNSBERG Lexicon (Work In Progress) §Orientation and Navigation · The DNA of Heaven, Part VII — lionsberg.wiki page name: Milestones Open: In ordinary delivery a milestone often carries a duration or a payment; here it has neither.