Calculating the Forward Path

Figure 7-5 shows a simple network with the forward path calculation.

Figure 7-5: Forward Path Calculation.

We must adopt a notation convention. The tasks will be shown in rectangular boxes; the earliest start date will be on the upper left corner, and the earliest finish will be on the upper right corner. The corresponding lower corners will be used for latest start and finish dates, respectively. Duration will be shown in the rectangle.

In the forward path calculation, notice the use of the earliest start dates. The basic rule is simple:

Earliest start date + Duration = Earliest finish date

Now we have to be cognizant of the various precedence relationships such as finish-to-start and finish-to-finish, etc. All but finish-to-start greatly complicate the mathematics and are best left to scheduling software. Therefore, our example networks will all use finish-to-start relationships. There is no loss in generality since almost every network that has other than only finish-to-start relationships can be redrawn, employing more granularity, and become an all finish-to-start network.

Working in the forward path with finish-to-start relationships, the rule invoked is:

Earliest start of successor task = Latest of the early finish dates of all predecessors

The final milestone from the forward path analysis is an "earliest" finish milestone. Again, unless explicitly shown, any final management reserve task of unallocated reserve task is not shown for simplicity. If it were shown, it would move out, or shift right, the final milestone to align with the program milestones from the business side of the balance sheet.

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