Intro to Project Management: Project Schedule Management Dependency Types Mandatory Discretionary External

What This Is

Dependency types are classifications of relationships between project activities, tasks, or milestones. Understanding these dependencies is crucial for effective project planning, scheduling, and risk management. For instance, consider building a bridge: the construction of the bridge's foundation is a mandatory dependency for building the bridge's superstructure. If the foundation isn't completed, the superstructure can't be built.

Key Terms & Formulas

• Mandatory Dependency: A relationship where one activity must be completed before another can start (e.g., building the bridge's foundation before building the superstructure).
• Discretionary Dependency: A relationship where one activity can be completed before another, but it's not necessary (e.g., painting the bridge's superstructure before installing the railings).
• External Dependency: A relationship where the completion of an activity depends on external factors, such as weather, supplier delivery, or regulatory approvals (e.g., waiting for a permit before starting construction).
• Lead: The amount of time an activity can be started before the predecessor activity is completed (e.g., 2 weeks before starting the superstructure construction).
• Lag: The amount of time an activity must wait after the predecessor activity is completed (e.g., 1 week after completing the foundation before starting the superstructure construction).
• Dependency Type Formula: Dependency Type = Mandatory (if predecessor is critical), Discretionary (if predecessor is not critical), or External (if dependent on external factors).
• Critical Path Method (CPM): A technique for analyzing dependencies to determine the minimum duration required to complete a project.
• Critical Path: The sequence of activities that determines the minimum duration required to complete a project.
• Float (or Slack): The amount of time an activity can be delayed without affecting the project's critical path or overall duration.

Step-by-Step / Process Flow

1. Identify Dependencies: Determine the relationships between activities, tasks, or milestones in your project.
2. Classify Dependencies: Classify each dependency as mandatory, discretionary, or external based on the project's requirements and constraints.
3. Schedule Dependencies: Schedule activities with mandatory dependencies first, followed by discretionary and external dependencies.
4. Monitor Dependencies: Continuously monitor dependencies and adjust the project schedule as needed to ensure timely completion.
5. Communicate Dependencies: Communicate dependencies to stakeholders, including team members, sponsors, and customers, to ensure everyone understands the project's critical path and timelines.

Common Mistakes

• Mistake: Assuming all dependencies are mandatory.
• Correction: Classify dependencies based on the project's requirements and constraints to ensure accurate scheduling and resource allocation.
• Mistake: Ignoring external dependencies.
• Correction: Identify and account for external dependencies, such as weather or supplier delivery, to ensure timely completion.
• Mistake: Not considering lead and lag times.
• Correction: Calculate lead and lag times to ensure accurate scheduling and resource allocation.

Exam Tips

• Tip: Be prepared to identify and classify dependencies in a given scenario.
• Tip: Understand the critical path method and its application in project scheduling.
• Tip: Be aware of the differences between mandatory, discretionary, and external dependencies.

Quick Practice Questions

1. If a project has a mandatory dependency between two activities, what does this mean for the project schedule? Answer: The project schedule must be adjusted to ensure the dependent activity is completed before the successor activity can start.
   Explanation: Mandatory dependencies require one activity to be completed before another can start.
2. If a project has a discretionary dependency between two activities, what does this mean for the project schedule? Answer: The project schedule can be adjusted to accommodate the dependent activity, but it's not required.
   Explanation: Discretionary dependencies allow one activity to be completed before another, but it's not necessary.
3. If a project has an external dependency on a supplier delivery, what does this mean for the project schedule? Answer: The project schedule is dependent on the supplier's delivery date, and any delays will impact the project timeline.
   Explanation: External dependencies are outside the project's control and can impact the project schedule.

Last-Minute Cram Sheet

• Mandatory Dependency: A relationship where one activity must be completed before another can start.
• Discretionary Dependency: A relationship where one activity can be completed before another, but it's not necessary.
• ⚠️ External Dependency: A relationship where the completion of an activity depends on external factors, such as weather or supplier delivery.
• Lead: The amount of time an activity can be started before the predecessor activity is completed.
• Lag: The amount of time an activity must wait after the predecessor activity is completed.
• Dependency Type Formula: Dependency Type = Mandatory (if predecessor is critical), Discretionary (if predecessor is not critical), or External (if dependent on external factors).
• Critical Path Method (CPM): A technique for analyzing dependencies to determine the minimum duration required to complete a project.
• Critical Path: The sequence of activities that determines the minimum duration required to complete a project.
• Float (or Slack): The amount of time an activity can be delayed without affecting the project's critical path or overall duration.