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exception of doing sloppy work, all of these methods may be acceptable. A reduction in scope must be
negotiated with your customer, of course.
• Scheduling is done initially on the assumption that you will have the resources you planned on
having. If people are shared with other projects or if you plan to use the same person on several tasks, you may find that you have overloaded her. Modern software generally will warn you that you have
overloaded your resources and may be able to help you solve the problem. CONVERTING ARROW DIAGRAMS TO BAR CHARTS
While an arrow diagram is essential to do a proper analysis of the relationships among the activities in a
project, the best working tool is the bar chart. Those people doing the work will find it much easier to know
when they are supposed to start and finish their jobs if you give them a bar chart. The arrow diagram in Figure
6-3 has been converted to a bar chart in Figure 6-4, making use of what was learned about the schedule from
the network analysis. Figure 6-4 Bar chart schedule for yard project.
The critical path in the bar chart is shown with solid black bars. Bars with float are drawn hollow, with a line
trailing to indicate how much float is available. The task can end as late as the point at which the trailing line
This is fairly conventional notation. Scheduling software always allows a bar chart to be printed, even though
a CPM network is used to find the critical path and to calculate floats. One caution: Many programs display
the critical path in red on a color monitor and may color tasks that have been started with green or blue. When
these are printed on a black-and-white printer, all of them may look black, implying that they are all critical
and confusing the people trying to read them.
It is usually possible to have the computer display shading or cross-hatching instead of color so that when the
schedule is printed in black and white, there will be no ambiguity.
Because most scheduling programs don’t create good bar charts when times are in minutes, the bar chart in
our example was created manually using Corel Draw. Printouts from scheduling packages usually look pretty
similar. CONSTRAINING THE END DATE
I have said previously that most projects have the end date imposed, by contract, market necessity, customer
need, or whatever. In addition, the start date for the project may be determined by further constraints—people
or equipment won’t be available until a certain time, perhaps.
Typically, when you pin down the start date for a project and calculate the end date for the network, the initial
solution won’t meet the required end date. That means that the project duration must be reduced. If you plug
the required finish into the last activity’s LF cell, rather than letting the computer make the EF and LF the
same (which is conventional analysis), the LF will actually be earlier than the EF for that activity. That means
it automatically has negative...
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- Fall '13