If you learned project scheduling from the PMBOK Guide, you learned six processes. The eighth edition has three. Nothing about the actual work disappeared, but the boundaries between the pieces did, and that matters if you are studying, writing training material, or maintaining a glossary that still lists the old process names as processes.
What the sixth edition had
In the PMBOK Guide, Sixth Edition, Project Schedule Management was a knowledge area with six numbered processes:
- 6.1 Plan Schedule Management
- 6.2 Define Activities
- 6.3 Sequence Activities
- 6.4 Estimate Activity Durations
- 6.5 Develop Schedule
- 6.6 Control Schedule
Each had its own inputs, tools and techniques, and outputs. Each was examinable on its own terms.
What the eighth edition has
The eighth edition is organised by performance domains rather than knowledge areas. Section 2.3 is the Schedule Performance Domain, and its process section (2.3.2) contains three processes:
- 2.3.2.1 Plan Schedule Management
- 2.3.2.2 Develop Schedule
- 2.3.2.3 Monitor and Control Schedule
The three that vanished did not vanish as work. They are now steps inside Develop Schedule. The guide names four of them (Figure 2-23):
- Define activities
- Determine sequence
- Estimate effort and duration
- Adjust
So defining activities is still the first thing you do, sequencing still comes second, and estimating still comes third. What changed is that they are no longer separate processes with their own input and output lists. The artifacts survive the move: the activity list, the activity attributes and the milestone list are named as the artifacts of step 1.
Why the merge makes sense
Scheduling was never a one-way pipeline. You define activities, sequence them, estimate them, look at the result, and then go back and change the activities because the result did not fit. The sixth edition acknowledged that iteration in prose while the numbering suggested a sequence of discrete processes. The eighth edition puts the loop inside one process and adds a fourth step, “adjust”, which is where the compression techniques and the balancing live. The structure now matches what schedulers actually do.
There is a cost to that, and it is worth saying plainly: the six-process model was easier to teach and easier to examine. A step inside a process has no input and output table of its own, so material that was built around those tables has to be rewritten rather than renumbered.
What to do with older material
Three practical consequences:
Study material. Anything that lists Define Activities, Sequence Activities or Estimate Activity Durations as processes is quoting the sixth edition. That does not make it wrong about the work, but it does not match the current structure.
Terminology. “Activity sequencing” as a term does not appear in the eighth edition at all. Neither does “Sequence Activities” as a process name. If you are checking vocabulary rather than concepts, check it against the edition you are actually being examined on.
Glossaries. This site is a case in point. It carries separate pages for these terms, written when they were separate processes, and they are being updated one by one to say where the concept lives now. The concept pages stay, because the work still exists and people still search for it by the old names. What changes is the framing: step, not process. See activity for how that reads in practice.
How to check this yourself
PMI publishes the table of contents of the eighth edition as a free PDF. It shows the performance-domain structure and confirms that section 2.3 is the Schedule Performance Domain, with 2.3.2 Processes running from page 48 to 55. It does not go down to the individual process level, so the three process names and the four steps of Develop Schedule have to be read in the guide itself, in section 2.3.2. PMI members have digital access; the sixth edition process numbers above are from section 6 of that edition.
Sources
- PMBOK Guide, Eighth Edition, table of contents (PDF, PMI)
- PMBOK Guide overview page (PMI)
- A Guide to the Project Management Body of Knowledge (PMBOK Guide), Eighth Edition, section 2.3.2 and Figure 2-23
- A Guide to the Project Management Body of Knowledge (PMBOK Guide), Sixth Edition, section 6
By Tom, PMP-certified since 2004. Last updated: September 2026.