prj566 project planning and management lecture: network diagrams
TRANSCRIPT
PRJ566 Project Planning and ManagementLecture: Network Diagrams
To Create a Plan You Need…
Work Breakdown Structure Dependencies Milestones The Network
Early/Late Start/End dates Slack/Float Critical Path
Task Dependencies Task A is said to be dependent on task B if
task B must precede task A (task B must be finished before task A can start)
Task B is called a predecessor of task A Task A can have many predecessors Only “immediate predecessors” are referred
to as predecessors
Milestone A task with zero time allocated to it. It is used as a “marker”; documentation. It is not assigned to anyone. Tasks can be dependent on milestones.
Network Diagram
A pictorial representation of the sequence in which the project work can be done
Shows the relationships (dependencies!) between tasks
MS Project creates network diagrams for you (=Gantt chart in MS Project)
Network Diagram
What order do I do these tasks in?
Network Diagram
1.1Measure Room
1.2Choose colors
1.3 Create Materials List
1.4 Create Estimate Sheet
1.5Review with client
2 Purchase Materials
3.1 Move Furniture
3.2 Wash Walls
3.3 Cover Floors
4 Paint Room
4 Paint Room
5.1 Clean up
5.2 Remove Floor Covers
Network Diagram = Gantt Chart1.1
1.2
1.3 1.4 1.5
2
3.1 3.2 3.3
4
5.1 5.2
Why are Network Diagrams important?
You can plan more effectively--you can see the relationship between activities
Easier to reschedule--you can see impact of changes
Allows you to monitor and control the project--compare it against baseline
Calculating Slack/Float What is the earliest/latest possible start of
each task?
Slack/Float time
Free Slack: range in which task can finish without causing delay in early schedule of immediate successors
Total Slack: range in which task can finish without causing delay to project completion
Late and Early Start/Finish
Early start/finish--earliest possible time that a task can start/finish without causing delay
Late start/finish--latest possible time that a task can start/finish without causing delay
Early Start/Finish
ES = latest finish of predecessors + 1
EF = (ES + duration) - 1
Early Start/Finish
1.1 1
1.2 2
1.3 1
1.4 3
1.5 1
2.1 2
2.2 1
2.3 1
2.4 2
5 81
2
2
2
6
6
6
3
2
4
1 5
7
6
6
9
Late Start/Finish
LF = earliest start of successors - 1 LS = (LF - duration) + 1
Late Start/Finish
1.1 1
1.2 2
1.3 1
1.4 3
1.5 1
2.1 2
2.2 1
2.3 1
2.4 2
5 81
2
2
2
6
6
6
3
2
4
1 5
7
6
6
9
98
6
7
7
7
7
755
4
4
4
4
3
2
11
Slack/Float time The delay (in units of time) that could be
tolerated in starting or completion time of a task without causing a delay in the project.
Slack time for a task = LF - EF
Slack Time = LF - EF
1.1 1
1.2 2
1.3 1
1.4 3
1.5 1
2.1 2
2.2 1
2.3 1
2.4 2
5 81
2
2
2
6
6
6
3
2
4
1 5
7
6
6
9
98
6
7
7
7
7
755
4
4
4
4
3
2
11
0
1
2
0
0
0
1
1
0
Critical Path
Longest duration path in network diagram
Sequence of tasks whose early and late dates are the same
Sequence of tasks with zero slack
Critical Path
1.1 1
1.2 2
1.3 1
1.4 3
1.5 1
2.1 2
2.2 1
2.3 1
2.4 2
5 81
2
2
2
6
6
6
3
2
4
1 5
7
6
6
9
98
6
7
7
7
7
755
4
4
4
4
3
2
11
0
1
2
0
0
0
1
1
0
Why care about Critical Path?
Tasks on this path need to be on time! If you know what they are you can track
them!
Critical Path
1.1 1
1.2 2
1.3 1
1.4 3
1.5 1
2.1 2
2.2 1
2.3 1
2.4 2
3.1 1 3.2 2 4 22.4 2
Critical Path
Dependencies with Lag Time
Lag time is time that must elapse after one task is completed before the dependent task can start
How do we show this in MSProject? Use the lag time variable in the task definition
These tasks fit all criteria
Longest duration path in network diagram Sequence of tasks whose early and late
dates are the same Sequence of tasks with zero slack
Why care about Critical Path?
Tasks on this path need to be on time! If you know what they are you can track
them! You can compress, adjust for maximum
benefit
Management Reserve
A contingency Budget of time--a time bank 5 to 10 % of total duration Withdraw from it when you run into
trouble Monitor it to see how much you’re using it
(overuse means trouble!)