prj566 project planning and management lecture: network diagrams

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!)