Page 162 - DCAP304_DCAP515_SOFTWARE_PROJECT_MANAGEMENT

Software Project Management

Notes  The sequence of activities whose early schedule and late schedule are the same
 The sequence of activities with zero slack or float.
The activities that define the critical path are called critical path activities. Any delay in a critical
path activity will delay the completion of the project by the amount of delay in that activity.
Critical path activities represent sequences of activities that warrant the project manager’s special
attention.

Earliest Start Time (ES) and Early Finish Time (EF)

The Earliest Start (ES) time for an activity is the earliest time at which all of its predecessor
activities have been completed and the subject activity can begin. The ES time can be set as
follows:
 The ES time of an activity with no predecessor activities is arbitrarily set to 1, the first day
on which the project is open for work.

 The ES time of activities with one predecessor activity is determined from the earliest finish
(EF) time of the predecessor activity.

 The ES time of activities having two or more predecessor activities is determined from the
latest of the EF times of the predecessor activities.
 The ES can also be used to calculate the earliest finish time of an activity. The earliest finish
(EF) of an activity is calculated as [(ES + Duration) – One time unit]. The reason for
subtracting the one time unit is to account for the fact that an activity starts at the beginning
of a time unit (hour, day, and so forth) and finishes at the end of a time unit. In other words,
a one-day activity, starting at the beginning of a day, begins and ends on the same day.

Example: Understand the Dependencies and Network Schedule
Look at Figure 8.6 and note that:

 Activity E has only one predecessor, activity C. The EF for activity C is the end of day 3.
Because it is the only predecessor of activity E, the ES of activity E is the beginning of day 4.
 Activity D has two predecessors, activity B and activity C. When there are two or more
predecessors, the ES of the successor, activity D in this case, is calculated based on the
maximum of the EF dates of the predecessor activities. The EF dates of the predecessors are
the end of day 4 and the end of day 3. The maximum of these is 4, and therefore, the ES of
activity D is the morning of day 5.

 Similarly, the EF and ES for other activities may also be calculated.
Figure 8.6: Forward Pass Calculations

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