Schedule Mechanics & Data
Fragnet
A fragnet is a small fragmentary network of activities representing a specific delay event, inserted into a schedule to model that event's impact on the project finish date.
Definition
Rather than trying to represent a delay event as a single generic activity, a fragnet models it with the same level of detail as the rest of the schedule -- its own sequence of sub-activities, durations, and logic ties into the existing network. Time Impact Analysis and Impacted As-Planned both work by inserting a fragnet at the appropriate point in a schedule and recalculating the network, so the resulting shift in the finish date reflects the fragnet's own real duration and logic rather than a rough estimate.
Example
An owner-directed design change is modeled as a three-activity fragnet -- design revision, owner review, and rework -- spliced between the activities it actually affects, rather than as one lump-sum delay activity.