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Schedule Network Diagram Construction

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The Schedule Network Diagram is a fundamental tool in the Critical Path Method (CPM) used for visualizing the sequence and interdependencies of all activities in a project. It provides a graphical representation of the project's activities, showcasing how each task is connected based on dependencies, which is crucial for identifying the critical path. Constructing this diagram involves listing all project activities, determining their durations, and identifying the dependencies between them (finish-to-start, start-to-start, finish-to-finish, and start-to-finish relationships)To construct a Schedule Network Diagram, project managers first develop an activity list derived from the Work Breakdown Structure (WBS). Each activity is assigned a unique identifier and estimated duration. Next, dependencies between activities are established, indicating the sequence in which tasks must be performed. This involves specifying predecessor and successor relationships, which can be complex in large projectsThe diagram is typically drawn using nodes (also known as boxes) to represent activities and arrows to depict dependencies. There are two main types of network diagrams: the Activity-on-Node (AON) method, which places activities on the nodes, and the Activity-on-Arrow (AOA) method, which places activities on the arrows. The AON method is more commonly used in CPM due to its simplicity and clarityBy visualizing the project's activities and their interrelationships, the Schedule Network Diagram aids in identifying the critical path—the longest sequence of activities that determines the project's minimum completion time. It also helps in spotting opportunities to optimize the schedule by rearranging activities, adjusting durations, or altering dependenciesIn summary, constructing a Schedule Network Diagram is a pivotal step in CPM scheduling. It transforms the abstract list of project activities into a coherent visual model, facilitating better understanding, communication, and management of the project schedule among stakeholders.

Schedule Network Diagram Construction Guide

What is Schedule Network Diagram Construction?

Schedule Network Diagram Construction is a critical project management technique used to graphically represent the sequence of project activities, their dependencies, and the logical relationships between them. It serves as a visual roadmap that illustrates how project tasks are connected and the order in which they must be completed.

Why is it Important?

Schedule Network Diagrams are essential for several reasons:

1. They provide a clear visual representation of project workflow
2. They help identify the critical path - the sequence of activities that determines the shortest possible project duration
3. They assist in determining task dependencies and constraints
4. They enable effective resource allocation and scheduling
5. They facilitate communication among project stakeholders
6. They help in identifying potential schedule risks and conflicts

How Schedule Network Diagrams Work

Schedule Network Diagrams represent project activities as nodes or arrows and show the relationships between these activities using connecting lines. The two primary methods are:

Activity-on-Node (AON) - Also known as Precedence Diagramming Method (PDM), this is the most common approach where activities are represented as boxes (nodes) connected by arrows showing dependencies.

Activity-on-Arrow (AOA) - In this approach, activities are represented as arrows, and nodes indicate the start and end of activities.

Types of Dependencies in Network Diagrams:

1. Finish-to-Start (FS): Activity B cannot start until Activity A is complete (most common)
2. Start-to-Start (SS): Activity B cannot start until Activity A starts
3. Finish-to-Finish (FF): Activity B cannot finish until Activity A finishes
4. Start-to-Finish (SF): Activity B cannot finish until Activity A starts (rarely used)

Steps for Creating a Schedule Network Diagram:

1. Identify all project activities
2. Determine the sequence and dependencies between activities
3. Draw the diagram using either AON or AOA method
4. Review and validate the diagram with stakeholders
5. Update the diagram as the project progresses

Exam Tips: Answering Questions on Schedule Network Diagram Construction

1. Understand the fundamentals: Be clear about the two main diagram types (AON/PDM and AOA) and their differences.

2. Know your dependencies: Memorize the four dependency types (FS, SS, FF, SF) and be able to identify them in diagrams or scenarios.

3. Practice drawing diagrams: Based on given activity lists and dependencies, practice creating network diagrams to reinforce your understanding.

4. Identify the critical path: Many questions will ask you to determine the critical path based on a network diagram.

5. Calculate float/slack: Understand how to calculate total float and free float for activities.

6. Look for trick questions: Exams may present diagrams with errors or missing dependencies - develop the habit of checking diagram validity.

7. Understand leads and lags: Know how to incorporate and calculate lead time (acceleration) or lag time (delay) in dependencies.

8. Use process of elimination: For multiple-choice questions, eliminate obviously incorrect answers first.

9. Read carefully: Pay attention to which diagram type the question is referring to.

10. Time management: Don't spend too much time on complex diagram questions - mark them and return if time permits.

Remember that Schedule Network Diagrams are key to understanding the Critical Path Method, so mastering this topic will help with many related project management concepts on the exam.

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PMI-SP - Critical Path Method (CPM) Example Questions

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Question 1

Which technique is most appropriate when constructing a schedule network diagram for activities with complex interdependencies?

Correct Answer: Precedence Diagramming Method (PDM) with multiple relationship types

The Precedence Diagramming Method (PDM) with multiple relationship types is the most appropriate technique for complex interdependencies because: 1. It allows for four different types of logical relationships: - Finish-to-Start (FS) - Start-to-Start (SS) - Finish-to-Finish (FF) - Start-to-Finish (SF) 2. These multiple relationship types provide flexibility to accurately model complex real-world scenarios and dependencies 3. PDM can handle leads and lags between activities The other options are less suitable because: Using only mandatory dependencies and finish-to-start relationships limits the ability to show complex relationships between activities Arrow Diagramming Method (ADM) is outdated and requires dummy activities, making it more complicated and less flexible Critical Path Method (CPM) is a calculation technique rather than a diagramming method, and focusing only on float calculations does not address the need for showing complex relationships between activities

Question 2

When establishing the Schedule Network Diagram sequence flow, what represents the most appropriate way to handle two parallel activities that must finish at exactly the same time?

Correct Answer: Use a Finish-to-Finish (FF) relationship with zero lag

Using a Finish-to-Finish (FF) relationship with zero lag is the most appropriate method to ensure two parallel activities end at exactly the same time. This relationship explicitly defines that both activities must complete simultaneously, which is the exact requirement in the question. The other options are problematic because: Applying a Finish-to-Start relationship with negative lag is an undesirable practice and can create scheduling complications and confusion in the network diagram. Creating a Start-to-Start relationship and adjusting durations does not guarantee simultaneous finish times during execution, as activities might experience different progress rates or delays. Inserting a milestone after both activities still requires some form of relationship between the activities themselves, and using only Finish-to-Start relationships doesn't ensure simultaneous completion.

Question 3

When creating a Schedule Network Diagram, what is the recommended approach for handling multiple paths that converge at a single milestone?

Correct Answer: Apply finish-to-finish relationships to preceding activities and validate total float

In a Schedule Network Diagram, when multiple paths converge at a milestone, the best practice is to apply finish-to-finish relationships to preceding activities and validate total float. This is the correct approach because: 1. Finish-to-finish relationships ensure all paths leading to the milestone are properly coordinated 2. Validating total float helps identify which paths are critical and which have slack 3. This method maintains the integrity of the network logic while ensuring realistic scheduling The other options are incorrect because: - Using mandatory constraints limits scheduling flexibility and can create artificial schedule pressures - Adding lag time arbitrarily to paths can distort the true project duration and create unnecessary delays - Using discretionary dependencies introduces subjective relationships that may not reflect true activity dependencies and can complicate resource management

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