In general, when schedule analysis is undertaken at a point in time during the project, it is considered prospective; when undertaken after-the fact, it is retrospective. Retrospective analysis undertaken to examine the schedule for later or earlier completion, identify related disruption and acceleration, and to apportion delay and gain and the associated additional costs is considered forensic schedule analysis.
Forensic Scheduling was acknowledged as a technical field distinct from project planning and scheduling in 2007 when AACE International issued Recommended Practice No. 29 Forensic Schedule Analysis (RP 29). RP 29 signaled the arrival of Forensic Scheduling as the knowledge successor to the prior art of Delay Analysis.
Leading the Way
In 2010, Dr. Gui Ponce de Leon, CEO & Managing Principal of PMA, in collaboration with other senior PMA leadership, published the “Guide to the Forensic Scheduling Body of Knowledge—Part 1,” which extends RP 29 and other standards. With over 20 years of experience collaborating on project work and forensic scheduling, they were uniquely positioned to compile existing and emerging principles and methods into this authoritative guide.
Once actual dates are introduced into a CPM schedule, the CPM scheduling algorithm ceases to function left of the data date. Total floats cannot be calculated with the CPM equation of late finish date (or actual finish) minus early finish date (or actual finish). With CPM unable to calculate total floats in the past, the critical path cannot be mathematically generated for the progressed portion of the schedule (left of the data date), or for the as-built schedule, without using work-around methods and potentially impairing accuracy of the analysis.
The graphical path method (GPM), pioneered and developed by Dr. Ponce de Leon, not only retains float left of the data date, but it is inherent to the GPM algorithm. This is because GPM calculates total floats from logic tie gaps rather than using early and late dates. In GPM, this value is referred to as forensic total float, and it continuously refreshes algorithmically, even as activities are re-planned right of the data date.
For more in-depth coverage of GPM, including the calculation of total floats and the location of the critical path left of the data date, browse the resources below, see the GPM tab, or visit PMA Technologies for more info.