Milestones, Activities, Tasks: A Work Breakdown That Matches How Facility Projects Run

Horizontal project tools give you infinitely nestable “tasks and subtasks” and call it flexibility. Facility delivery teams keep rebuilding the same three levels anyway, because the levels mean something different to different audiences:

• Milestones are the steering-committee unit — reviewed monthly, tied to phase gates.
• Activities are the crew unit — planned weekly, owned by a discipline lead.
• Tasks are the field unit — done, verifiable, assignable to a person, and the only level with a manual percent.

Make every level first-class

In legacy trackers, milestones and activities are dumb containers — a name and a sum. In practice each deserves its own owner, target date, status, and notes: “loop checks” being blocked is milestone-level information even when individual loop tasks are merely “not started”.

Numbering: positional, display-only

The dotted number (2.1.3.4 — phase.milestone.activity.task) is how a crew talks about work, so keep it — but derive it from position and never store it as identity. Renumbering after a reorder is then a display refresh, not a data migration, and “insert a milestone above 2.3” stops being a find-and-replace incident. Milestone numbers reset within each phase, because that's how people actually say it: “OR milestone two”, not “milestone fourteen”.

Where the percent lives

One rule keeps the whole structure honest: manual percent complete exists only at the leaf. Everything above is a weighted average, computed, with the math inspectable. The three levels give you the right places to put weights, owners, and status; the leaf-only rule keeps the summary from becoming an opinion.

This MAT breakdown — with first-class levels, positional numbering, and computed rollups — is the data model Fieldcurve is built on, because it's the one facility teams already think in.