Identification of Activities
Every CPM schedule is built from one honest unit: the activity. Get the activities right — single scope, one owner, measurable, right-sized — and the schedule can be trusted; get them wrong and nothing downstream holds. Built on AACE 23R-02.
What an activity actually is
A schedule is not a list of dates — it's a model of work. The unit of that work is the activity.
"Identifying activities" is the step where you translate the project's scope into a list of work elements the CPM can reason about. It comes after the WBS and before logic and durations — and it quietly determines how useful the whole schedule will be.
From scope to WBS to activities
Activities aren't invented from thin air — they're decomposed from the project scope through the Work Breakdown Structure. The WBS breaks the project into progressively smaller deliverables; the lowest level (the work package) is then broken into the activities needed to produce it.
What makes a good activity
Not every line on a bar chart is a sound activity. A well-formed activity passes a few simple tests:
- Single, definable scope — it represents one identifiable piece of work, describable in a clear verb-noun ("Pour slab L2", not "Civil works").
- One owner / responsibility — a single party (crew, trade, subcontractor) is accountable for it, so progress and delay can be attributed.
- Measurable progress — you can tell how complete it is, by quantity installed, not by gut feel.
- Has a start and a finish — it consumes time between two points; it can take predecessors and successors (next lesson's logic).
- Right-sized duration — long enough to be meaningful, short enough to control — typically within one or two reporting periods.
Activity types
Most lines are ordinary work, but a few special types do specific jobs in the network.
| Type | What it is | Duration |
|---|---|---|
| Task / production | Ordinary work that installs scope — the bulk of the schedule | > 0 |
| Milestone | A point in time marking a key event (start, finish, handover) — no work | 0 |
| Level of Effort (LOE) | Sustaining work with no deliverable of its own (e.g. project management, supervision) — spans other work | follows others |
| Hammock / summary | A roll-up spanning a group of activities, for reporting — derives its dates from them | derived |
Granularity — how fine is right?
The hardest judgment in activity identification is granularity: how finely to break the work down. Too coarse and the schedule can't be controlled; too fine and it becomes unmanageable busywork that nobody updates.
| Too coarse | Too fine | |
|---|---|---|
| Symptom | "Build structure — 120 days" | "Tighten bolt row 7" × 4,000 |
| Problem | Can't see status, sequence, or where delay sits | Impossible to update; noise drowns the signal |
| Result | A schedule that looks fine while the project drifts | A schedule nobody maintains, so it goes stale |
Ten things to remember
- The activity is the atomic unit of the schedule — logic, durations, resources all attach to it.
- The schedule is never better than its activities — vague activities poison every later layer.
- Activities are decomposed from the WBS work packages — not invented ad hoc.
- The 100% rule: activities cover all of a work package's scope — no orphans, no overlaps.
- A good activity has single scope, one owner, measurable progress, a start/finish, and a right-sized duration.
- Name with verb-noun-location — "Install ductwork — L3 East", never "Misc."
- Know the types: task, milestone (0 duration), LOE, hammock — and use the special ones sparingly.
- Too coarse hides status and delay; too fine becomes unmaintainable noise.
- Size to your control need and reporting cycle — roughly one to two update periods per activity.
- One activity, one work front, one crew — the cleanest unit to plan and to status.
Glossary
- 100% rule
- The activities under a work package must account for all of its scope, with no overlap.
- Activity
- A discrete element of work with a start, finish, and (usually) resources — the schedule's base unit.
- Granularity
- How finely work is broken into activities — balanced for control vs maintainability.
- Hammock
- A summary activity whose dates derive from a group it spans.
- Level of Effort (LOE)
- Sustaining work with no standalone deliverable; spans other activities.
- Milestone
- A zero-duration marker for a key event or date.
- WBS
- Work Breakdown Structure — the deliverable-oriented decomposition of project scope.
- Work package
- The lowest WBS level, decomposed into activities.