Explainer
A dependency is something one piece of work needs from another before it can start or finish. Here are the four types, examples from system programmes and how to stop dependencies quietly delaying go live.
By Christopher Fagan, Managing Partner, PEF Consulting Partners
A dependency is a relationship between two pieces of work where one relies on the other. Inside a project, dependencies link tasks in the schedule. Between projects, or with outside parties, they are commitments someone else must deliver for your plan to hold, and that is where most of the risk sits.
| Type | Meaning | Example |
|---|---|---|
| Finish to start | B cannot start until A finishes | Testing cannot start until the build is complete |
| Start to start | B cannot start until A starts | Data cleansing starts once data extraction starts |
| Finish to finish | B cannot finish until A finishes | Training cannot finish until the final design is signed off |
| Start to finish | B cannot finish until A starts | The old system cannot be switched off until the new one is running |
Internal dependencies sit within your control, such as one workstream waiting for another. External dependencies sit outside it: a supplier release, a regulatory decision, an industry programme milestone or a data feed from another organisation. Every external dependency needs an owner on your side and an agreed date on theirs.
On programmes with several projects, a simple dependency map showing which project gives what to which, and when, is often the most useful single picture the PMO can produce. It is also the first thing to check when a programme starts slipping for no obvious reason.
Related reading: the RAID log template, the project plan template, what a PMO does, the decision log template.
Relationships between pieces of work where one relies on another, either tasks within a project or commitments between projects and outside parties.
Finish to start, start to start, finish to finish and start to finish. Finish to start is by far the most common.
A supplier’s software release, a regulator’s decision, an industry programme milestone or a data file from another organisation that your plan needs by a certain date.
A list of the dependencies a project relies on or provides, each with an owner, counterparty, date and status. It is often kept as the D in a RAID log.
If your programme keeps slipping by a week at a time, map its external dependencies. The cause is usually there.