PRJ566 Project Planning & Management

Dependencies, Network Diagrams & Critical Path

Agenda

Where are we? Network Diagrams Critical Path

Where are we?

Identified work breakdown structure (WBS) – activities and tasks

Estimated tasks Assigned resources Assigned dependencies

Agenda

Where are we? Network Diagrams Critical Path

Network Diagram

A pictorial representation of the sequence in which the project work can be done

Shows the relationships (dependencies) between tasks

Network Diagram

What order to 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

Agenda

Where are we? Network Diagrams Critical Path

Critical Path

A Network Diagram is a tool for identifying all the possible paths through a project. The paths are dictated by the dependencies.

To determine critical path in a network diagram, identify all the possible paths through the network diagram and add up the durations of the activities that lie along those paths.

The path with the longest duration time is the critical path.

Critical Path

Given a list of tasks and dependencies as shown below, a network diagram can be constructed.Task ID Description Duration Predec

essor

0 Start 0 None

1 Find Client 3 days 0

2 Find System 2 days 0

3 Gather Requirements 6 days 1,2

4 Create Use Case Diagram 2 days 3

5 Create Use Case Descriptions 5 days 3

6 Review with User 1 day 1,4

Network Diagram

0 Start

2Find System

2

1Find Client

33

GatherRequirements

6

4Create Use

Case Diagram2

6 Review

With User1

5Create Use Case

Descriptions5

Slack/Float time

Need to understand the slack time of an activity.

Slack time: The difference between the late finish and

early finish of an activity.

Network Diagram

0 Start

2Find System

2

1Find Client

33

GatherRequirements

6

4Create Use

Case Diagram2

6 Review

With User1

5Create Use Case

Descriptions5

If task 1 above takes 3 days and task 2 takes 2 days, then there is 1 day of slack (free slack).

Calculating Critical Path

To calculate critical path: Total the durations of every path. Largest value is the critical path.

Critical Path

d

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

0

1

2

0

0

0

1

1

0

duration

slack

Calculating Critical PathTask/Activity Durations Total

1.1+1.2+1.5+2.1+2.4 1+2+1+2+2 8

1.1+1.2+1.5+2.2+2.4 1+2+1+1+2 7

1.1+1.2+1.5+2.3+2.4 1+2+1+1+2 7

1.1+1.3+1.5+2.1+2.4 1+1+1+2+2 7

1.1+1.3+1.5+2.2+2.4 1+1+1+1+2 6

1.1+1.3+1.5+2.3+2.4 1+1+1+1+2 6

1.1+1.4+1.5+2.1+2.4 1+3+1+2+2 9

1.1+1.4+1.5+2.1+2.4 1+3+1+1+2 8

1.1+1.4+1.5+2.3+2.4 1+3+1+1+2 8

Critical Path!

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

0

1

2

0

0

0

1

1

0

Task 1.2 can slip by 1 day;Task 1.3 can slip by 2 days

Task 2.2 can slip by 1 day;Task 2.3 can slip by 1 day

duration

slack

Critical Path

Fortunately MSProject automatically calculates the Critical Path. Once you know which tasks are on the Critical Path, you can track these tasks very closely.

Once you create your Gantt Chart in MSProject, click on Format, Gantt Chart Wizard and select Critical Path and then finish. MSProject formats your project plan to show the Critical Path in Gantt Chart view.

The Critical Path is automatically calculated!

Critical Path

Longest duration path Sequence of tasks whose early and late

dates are the same Sequence of tasks with zero slack Drives the completion date of the project

Critical Path

The Critical Path tells you what tasks are critical.

In other words, if you change the duration or start and end date of the task on the critical path, it will affect the completion date.

Critical Path Sample – Gantt Chart