Milestones and benchmarks are zero duration events that are used to represent key dates or moments in the schedule. Two types are available: a start milestone/benchmark, and a finish milestone/benchmark. The start type aligns to the beginning of the day or time unit (by default, 9:00 am), and should be used for events which will precede an activity or represent an initiation; the finish type aligns to the end of the day or time unit (by default, 5:00 pm), and should be used for events which will succeed an activity or represent a termination. In addition, both milestones and benchmarks can be represented by a variety of shapes; however, each one has its own set of behaviors.
Milestones, like activities, will track along with the network, once they’ve been linked to any predecessors or successors. In addition, a start milestone will snap to its earliest successor and a finish milestone will snap to its latest predecessor, always maintaining a zero gap link. If a start milestone has no successors (for example, if it’s been linked to an activity that precedes it in time), it will not snap and erase any gap, but it will continue to track. If a finish milestone has no predecessors, it will also not snap but continue to track. While such relationships are discouraged and illogical, they may serve as a workaround snapping, where desired.
Benchmarks, unlike activities and milestones, will remain fixed at whatever date they are placed, regardless of whether or not they’ve been linked to any predecessor or successors. This means that even as an activity is pushed earlier or later than it, a negative gap link will open up as it passes. Although by default, benchmarks show up red, they are not and cannot be critical. This is because they do not have any float or drift themselves. In fact, any activities connected to the benchmark will have their float and drift calculated to the benchmark rather than to the project start and completion. This allows benchmarks to be used to divide up float and allocate it to different stages instead of having it accumulate undisturbed from schedule completion.
NOTE: If you’re planning on running a GPM risk analysis, benchmarks should be converted to milestones for best practice. For more info, see [bookmark postid=”11620″ anchor=”converting”]Converting Between Milestones and Benchmarks[/bookmark].
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