Schedule Network Diagrams

Schedule Network Diagrams Guide

What Are Schedule Network Diagrams?

Schedule Network Diagrams are visual representations that show the logical relationships and dependencies between project activities. They are critical tools in project scheduling that illustrate how activities are connected and the sequence in which they must be performed.

Why Schedule Network Diagrams Are Important

Schedule Network Diagrams are essential because they:

• Help identify logical relationships between activities
• Reveal the critical path of the project
• Assist in determining early and late start/finish dates
• Enable calculation of float or slack time
• Aid in resource allocation and optimization
• Support schedule compression techniques when needed
• Provide a visual framework for schedule management

Types of Schedule Network Diagrams

1. Precedence Diagramming Method (PDM) - The most common approach, also known as Activity-on-Node (AON). Activities are represented as nodes (boxes), with arrows showing dependencies.

2. Arrow Diagramming Method (ADM) - Also called Activity-on-Arrow (AOA). Activities are represented as arrows, with nodes marking the start and end of activities. Less commonly used in modern project management.

Types of Dependencies in Network Diagrams

• Finish-to-Start (FS): Activity B cannot start until Activity A finishes (most common)
• Start-to-Start (SS): Activity B cannot start until Activity A starts
• Finish-to-Finish (FF): Activity B cannot finish until Activity A finishes
• Start-to-Finish (SF): Activity B cannot finish until Activity A starts (rarely used)

How Schedule Network Diagrams Work

1. Creating the Diagram:
• List all project activities
• Determine dependencies between activities
• Draw nodes (boxes) for each activity
• Connect nodes with arrows showing dependencies
• Add information like activity duration and resource requirements

2. Forward Pass:
• Start from the beginning and move forward through the network
• Calculate Early Start (ES) and Early Finish (EF) dates for each activity
• EF = ES + Duration - 1

3. Backward Pass:
• Start from the end and move backward through the network
• Calculate Late Finish (LF) and Late Start (LS) dates for each activity
• LS = LF - Duration + 1

4. Determining Float:
• Float (or slack) = LS - ES or LF - EF
• Activities with zero float are on the critical path

Exam Tips: Answering Questions on Schedule Network Diagrams

1. Know the terminology:
• Familiarize yourself with terms like predecessor, successor, critical path, float, lag, lead, milestone, and constraint

2. Understand dependency types:
• Be able to identify and apply FS, SS, FF, and SF relationships
• Recognize which type is most common (FS) and which is rarely used (SF)

3. Critical path calculations:
• Practice calculating ES, EF, LS, LF, and float
• Remember that the critical path has zero float
• The critical path determines the minimum project duration

4. Drawing practice:
• Practice drawing simple network diagrams from activity lists
• Ensure arrows point in the correct direction to show logic

5. Common question formats:
• Identifying the critical path given a network diagram
• Calculating float for specific activities
• Determining impacts of delays on project schedule
• Analyzing effects of adding resources to activities
• Finding the earliest project completion date

6. Contextual understanding:
• Connect network diagrams to other scheduling concepts (Gantt charts, resource histograms, etc.)
• Understand how changes in scope impact the network diagram

7. When answering questions:
• Draw the network diagram if one isn't provided
• Label all nodes with activity names/IDs
• Show your calculations step by step
• Double-check your math, especially with complex networks

Example Question Approach

Question: "Given the network diagram, which activities are on the critical path?"

Approach:
1. Examine the diagram for activities with zero float
2. If float values aren't given, calculate ES, EF, LS, LF for each activity
3. Determine float for each activity (LS - ES or LF - EF)
4. Identify activities with zero float - these form the critical path
5. Trace the path from start to finish to verify your answer

Remember that schedule network diagrams are vital tools for project time management. They help visualize the project flow, identify potential bottlenecks, and determine the minimum project duration. Mastering this topic is crucial for success in the PMI-SP certification exam.