Realistic Schedule Management: Lead, Lag, and Logical Sequencing

PMBOK v8 Definition

Realistic Schedule Management is the practice of creating a project schedule that accurately reflects achievable timelines by using appropriate logical relationships and lead/lag time between activities. The key benefit is that it defines the logical sequence of work to obtain the greatest efficiency, given all of the project constraints. Every work package and activity, except for the first and last, should be connected to at least one predecessor and at least one successor activity with an appropriate logical relationship.

Why It Matters for the Exam

This concept appears frequently in PMI exam questions related to Schedule Management, particularly in scenario-based questions where you must determine whether to use lead or lag time to create a realistic schedule. Exam questions often test your ability to recognize when a schedule is unrealistic due to missing dependencies or incorrect application of leads and lags.

Key Points to Remember (for the exam)

• Core Principle: Every activity (except first and last) must have at least one predecessor and one successor with appropriate logical relationships

• Logical Relationship Types: Finish-to-Start (FS), Start-to-Start (SS), Finish-to-Finish (FF), Start-to-Finish (SF) – FS is the most common

• Lead Time: Acceleration of a successor activity – allows successor to start before predecessor finishes (negative lag)

• Lag Time: Delay between predecessor and successor – imposes a waiting period (positive lag)

• Schedule Levels: Sequence can be determined at control account, work package, or activity level depending on degree of decomposition

• Progressive Elaboration: With shrinking timelines, detailed schedules may be developed progressively as the project unfolds, even in predictive approaches

• Rolling Wave Planning: Key technique for progressively detailing schedule activities in the overall schedule model

Typical PMI Exam Example

A project manager is developing the project schedule for a construction project. The concrete foundation must cure for 7 days before framing can begin. What should the project manager apply between these activities? Answer: Lag time (7-day delay) with a Finish-to-Start relationship.

PMI Exam Traps

• Trap: Confusing lead with lag

  • Reality: Lead accelerates (negative lag), lag delays (positive lag)

• Trap: Thinking all activities need only one dependency

  • Reality: Every activity (except first/last) needs both predecessor(s) AND successor(s)

• Trap: Assuming schedule detail must be complete upfront

  • Reality: Rolling wave planning allows progressive detailing as the project unfolds

• Trap: Confusing activity sequencing with duration estimating

  • Reality: Sequencing defines logical order; duration estimating determines time needed for each activity

Important PMI Connections

Quick Review Questions

1. What is the difference between lead time and lag time in activity sequencing?

2. Which logical relationship type is most commonly used in project scheduling?

3. When using an adaptive life cycle, what technique helps minimize scope creep by forcing the team to process essential features first?

4. At what levels can activity sequence be determined, depending on the degree of decomposition?

5. Why might a project manager use rolling wave planning instead of developing a detailed schedule upfront?

PMBOK v8 Reference

Section 2 – Project Management Performance Domains (Schedule Performance Domain)