Schedule Updating and Project Control - Construction Project Scheduling and Control - page 161

This information can be further subdivided into past and current cate-
gories, in which past represents information about work that occurred prior
to the previous update. Such information is considered history and must not
be changed during the present update. 1 Current represents information about
work that has occurred between the last update and the current update. This
category is the main focus area for updating past information.
2. Future information: The future category comprises any changes to the sched-
ule or schedule-related items, such as the following:
a. Any activities that have been added, along with their information (duration,
logic, budget, resources, constraints, etc.)
b. Any activities that have been deleted (the scheduler must be sure to maintain
proper logic after the deletion)
c. Activities that have changed in duration, logic, budget, resources, con-
straints, or otherwise
d. Any change to the imposed finish date for the entire schedule or the con-
straint date for certain milestones
e. Any schedule-related, but not activity-specific, change, such as a change in
the cost or availability of resources, a change in calendar workdays, or a
change in responsibility (e.g., a subcontractor took over a portion of the
general contractor's work, or a subcontractor was replaced)
Note that added or deleted activities can also occur in the past . This can
happen if a change order arrives on short notice: the activity is approved and
added to the schedule and then performed (started/finished) between two
updates, that is, after the previous update and before the current one.
Figure 7.1 defines the three information zones discussed above: “past” (prior to
or to the left of the previous data date), “current” (between the previous data date and
the current data date), and “future” (after or to the right of the current data date).
Future changes are of two types:
1. Logic-driven changes: Logic-driven changes are those that are not made directly
by the scheduler but that occur as a result of changes in planned dates or logic.
For example, the four activities shown in Figure 7.2a were planned to over-
lap and take 14 days overall. When updating, four days after the first activity,
Framing, has started, it is found that the Framing activity will take 2 more days
than originally planned (see Figure 7.2b). As a result, succeeding activities will
be delayed by the same amount, that is, 2 days. It is similar to the domino
effect: a delay in one activity will trigger a delay in the succeeding activities.
1 Although sometimes project managers “revise” dates or other data that were reported previously, this
practice may be considered a falsification of records if the owner is not fully informed of such revisions.