A Dependency between two Milestones means that the destination Milestone cannot be completed until the source Milestone is complete. In both cases you can start the destination Milestone before the source Milestone is complete.
- A Dependency between two Tasks means that the destination Task cannot be started until the source Task is complete.
- A Dependency between a Task and a Milestone means that the destination Milestone cannot be completed until the source Task is complete.
- A Dependency between a Milestone and a Task means that the destination Task cannot be started until the source Milestone is complete.
A Dependency can also be either ‘internal’ or ‘external’; an internal Dependency is internal to the Plan (i.e. it can be shown as an arrow between two Milestones/Tasks in the Plan) whilst an external Dependency is between two Milestones/Tasks in different Plans (either in the same WBS or in another WBS entirely). An external Dependency is shown by a ‘stub’ arrow that does not originate from or terminate at another Milestone in the Plan. Placing the cursor over an external Dependency arrow (incoming or outgoing) will display the name of the ‘other’ plan and milestone involved in the Dependency.
Therefore, that there can be four different types of Dependency, viz.
Incoming Internal
Outgoing Internal
Incoming External
Outgoing External
Dependency arrows in Red are ‘impossible’, because the required completion date of the dependent Milestone/Task precedes that of the source Milestone/Task.
Overlapping Dependency lines can be moved by clicking and dragging on them, so improving visibility.
