In May 2003, O’Brien, et al. could not see the logic in many CPM schedules. In the intervening years, a number of scheduling experts, including this author, have posited that the critical path method (CPM) is past its prime. However, seemingly, nothing much has changed as mainstream scheduling practice continues to be hindered by overly detailed, flawed schedules that stakeholders cannot decipher―much less collaborate on―in the face of the Internet social revolution that cries out for more engaging, transparent, and “stakeholder-centric” processes. In this keynote, Dr. Gui presents to professionals in Peru the graphical path method introduced in 2008 in response to O’Brien’s plea for a return to scheduling fundamentals.
Dr. Gui Ponce de Leon, PE, PMP, LEED AP
Presented at 2015 AACE International event, Third Congress of Cost Engineering
October 24th, 2015
What is CPM Scheduling?
A networking method that, following any input for any activity, logic tie, or milestone, requires a forward pass and a backward pass for the entire network as a preceding step to obtain an output of the schedule. Date constraints are required to schedule activities on planned dates. Neither total floats nor the as-built critical path can be calculated left of the data date.
What is GPM Scheduling?
The graphical path method (GPM) is similar to the critical path method (CPM) but embodies a simpler scheme of thought in ways CPM can’t. GPM is a graphical and visualization method that, without a forward or backward pass, kinetically refreshes the schedule where impacted as the user adds/deletes/revises/repositions activities, logic ties, and milestones. Activities on planned dates may float back (in GPM lexicon, have drift). Total floats and the as-built critical path are algorithmically calculated left of the data date.
GPM as Applied in Planning/Scheduling
- Visualization is enabled by a new time-scaled logic diagramming method (LDM) that combines the strengths of arrow & precedence diagrams
- Activities may be on planned dates without resorting to date constraints or preferential lags
- An activity on GPM planned dates can drift back (to the early start date) and may float forward (to the late finish date)
- The kinetic interface is enabled by GPM self-healing and scheduling algorithms, which─as a planner is physically manipulating activities─restore the impacted aspects of the network to their correct mathematical state
- Both forward (push) planning and backward (pull) planning are enabled
- In every schedule update, total floats left of the data date are calculated, which allows algorithmic identification of the then-existing as-built critical path