02-01-2013, 10:37 AM
ACTIVITY NODE CALCULATIONS
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Activity node techniques are basic techniques in schedule management. They
were first introduced in space projects during the 1950’s. Today almost every
project management software has an activity node calculation feature.
When doing activity node diagrams, project’s activities (list of tasks), their
dependencies and durations need to be known.
Typically when activity node diagrams are built, every project activity is started
as early as possible. That way the earliest start and the earliest finish of each
activity can be calculated. In addition the longest path of dependent activities
(= critical path) and the total duration of the project can be detected.
In the second phase activities can be scheduled to the latest possible start, so
that the total duration of the project doesn’t change. That way the latest start
and the latest finish of each activity can be obtained.
The difference of each activity’s earliest and latest start tells how much slack
(float) there is available for each activity.
Start to finish calculation (earliest start (ES))
1. The first activity is given value ES = 0. This is also the earliest start (ES) of
every activity that starts at the same time as the first activity.
2. Earliest finish (EF) of the first and all the other activities, which start at the
same time, is calculated. They are obtained by adding the duration of the
activity to the earliest start (EF = ES +D)
3. Timing of the succeeding activity: