The Network Diagram

When to Do What?  Carrying out one activity after the other may result in project completion, but it will take the longest possible time  If any activities can be worked on concurrently then the project duration will be shortened  How to build the project schedule? COPYRIGHT TOM SULZER © 2016

Gantt Charts  Activities are represented by horizontal bars along a time line  Bar length indicates the duration of the activity  Useful for simple projects  Insufficient information is used for efficient planning t COPYRIGHT TOM SULZER © 2016

Network Diagram  Contains information on  Activity precedence  Activity dependence  Start times  Finish times  Embodies  Constraints COPYRIGHT TOM SULZER © 2016

Information Required  Each activity (except for the start and ending activities) must have a predecessor and a successor  Activities may have dependency relationships between them  Activity durations and other time-related data COPYRIGHT TOM SULZER © 2016

Dependency Activity 1 Activity 2 Activity 1 Activity 2 Activity 1 Activity 2 When 1 finishes, 2 can start When 1 finishes, 2 may finish When 1 starts, 2 may start When 1 starts, 2 may finish COPYRIGHT TOM SULZER © 2016

Precedence Activity 1Activity 2 Activity 1 Activity 2 Activity 3 2 follows the end of 1 3 follows the end of 1 and 2 2 and 3 follow the end of 1 COPYRIGHT TOM SULZER © 2016

Constraints  Technical constraints – force predecessor- successor relationships with finish-start dependencies  Management constraints – manager forces finish-start on two activities rather than concurrency because of a need to review one activity before using it in the other COPYRIGHT TOM SULZER © 2016

The Schedule Activity A D Activity B D Activity C D Activity D D Activity F D Activity E D EF ES LS LF COPYRIGHT TOM SULZER © 2016

Durations Activity A 2 Activity B 4 Activity C 6 Activity D 5 Activity F 2 Activity E 3 EF ES LS LF COPYRIGHT TOM SULZER © 2016

Forward Pass to Calculate ES, EF Activity A 2 Activity B 4 Activity C 6 Activity D 5 Activity F 2 Activity E LS LF COPYRIGHT TOM SULZER © 2016

Backward Pass to Calculate LS, LF Activity A 2 Activity B 4 Activity C 6 Activity D 5 Activity F 2 Activity E COPYRIGHT TOM SULZER © 2016

Example: Activity A 2 Activity B 2 Activity D 3 Activity C 5 Activity F 4 Activity E COPYRIGHT TOM SULZER © 2016

Example – How did we get the #s? Activity A 2 Activity B 2 Activity D 3 Activity C 5 Activity F 4 Activity E COPYRIGHT TOM SULZER © 2016

Computing the Slack A (S=0) 2 B (S=2) 4 C (S=0) 6 D (S=0) 5 F (S=0) 2 E (S=2) Activity Slack = LF-EF (or LS-ES) COPYRIGHT TOM SULZER © 2016

Computing Slack Cont. Activity A 2 Activity B 2 Activity D 3 Activity C 5 Activity F 4 Activity E (S=0) (S=2) (S=0) COPYRIGHT TOM SULZER © 2016

The Critical Path Activity A 2 Activity B 2 Activity D 3 Activity C 5 Activity F 4 Activity E (S=0) (S=2) (S=0) COPYRIGHT TOM SULZER © 2016

Using the Critical Path  Note that a delay in an activity on the Critical Path will delay the whole project  Note that activity durations are estimates: near critical path activities (with little slack) can become critical as duration time becomes better known COPYRIGHT TOM SULZER © 2016

Adding in Lag and Reserves  Waiting time (for a third party to respond/deliver) can be modeled as an activity  Do not pad activity estimates (work expands to fill the time allocated)  Make final activity of project the “management reserve” – time to controlled and monitored by the project manager. COPYRIGHT TOM SULZER © 2016

Project Software  Software can manage estimates of durations with variability (Earliest, Most Probable, Worst)  Allows computation of ‘probability” of finishing project in a certain time. COPYRIGHT TOM SULZER © 2016

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