A formal identification and re-sequencing process for developing sequencing alternatives in CPM schedules

Construction planners face many scheduling challenges during the course of a project. Limitations in time and resources frequently require planners to re-sequence existing activity sequences to expedite milestone or bottleneck activities. Re-sequencing activities within a CPM network, however, is time-consuming and error-prone because planners find it difficult to know which activities may be delayed and what the implications are to other activities once an activity is delayed. This paper presents a formal identification and re-sequencing process that supports the rapid development of sequencing alternatives in construction schedules. The identification process identifies activities in a CPM schedule that when delayed will expedite a project-critical activity. The re-sequencing process ensures that any sequencing conflicts that occur while re-sequencing activities are correctly resolved. The process builds on a constraint ontology that provides domain-specific representation of sequencing rationale for construction activities. The process also utilizes a classification mechanism that provides the heuristics to infer the role and "status" (i.e., whether an activity may or may not be delayed) between activities. The entire process ensures that all possible re-sequencing solutions are explored and developed consecutively. Validations performed using a prototype system, "Constraint-loaded CPM" (CLCPM), demonstrate improvement in planners' ability to understand the schedule logic and quickly devise alternative sequencing scenarios for execution.