A method of expressing the dependence of distinct activities for project management (see PERT). The chart is drawn as a weighted directed graph where each edge represents a specific activity and its weight is the time required to complete that activity. The activity can only be started when those edges (activities) incident to it have been completed. The chart has one start point and one termination point.

The critical path for time to project completion is calculated together with the float, earliest start, and latest start times on individual activities. Some PERT tools allow different types of resource to be allocated to an activity, with limits on total resource of each type, and for ‘hammocks’ (dummy activities) to be used to monitor project milestones and resource usage. See also activity network, critical path method.