Best Practice 5: Verifying That the Schedule Can Be Traced Horizontally and Vertically

Best Practice 5: The schedule should be horizontally traceable, meaning that it should link products and outcomes associated with other sequenced activities. Such links are commonly referred to as “hand-offs” and serve to verify that activities are arranged in the right order for achieving aggregated products or outcomes. The schedule should also be vertically traceable—that is, varying levels of activities and supporting subactivities can be traced. Such mapping or alignment of levels enables different groups to work to the same master schedule.

Horizontal traceability demonstrates that the overall schedule is rational, has been planned in a logical sequence, accounts for the interdependence of detailed activities and planning packages, and provides a way to evaluate current status. Schedules that are horizontally traceable depict logical relationships between different program elements and product handoffs. Horizontally traceable schedules support the calculation of activity and milestone dates and the identification of critical and near-critical paths.

Horizontal traceability applies to both an individual project schedule and the entire IMS, which may consist of multiple files. A horizontally traceable IMS includes complete logic from program start to program finish and fully integrates the entire scope of work from all parties in the program. Horizontal traceability ensures that forecasted dates within the schedule will be determined by network logic and progress to date rather than by artificial constraints. Any logic errors in the summary, intermediate, and detailed schedules will make dates between schedules inconsistent and will cause managers and activity owners to differ in their expectations.

Detail activities, milestones, and planning packages in a horizontally traceable schedule are linked to one another, preferably through straightforward finish-to-start logic at the detailed level that represents the required inputs and outputs in a planned effort. Milestones representing key decisions or deliverables should have each predecessor activity traced and validated to make certain that they are directly related to accomplishing the milestone.

In particular, “giver/receiver” (G/R) milestones, common when multiple schedules are linked to form the IMS, must be clearly identified and logically linked between schedules. Giver/receiver milestones represent dependencies between schedules, such as hand-offs between integrated product teams and delivery and acceptance of government-furnished equipment. For example, a production schedule may include “receiver” milestones from outside suppliers representing the delivery of material and “giver” milestones representing the delivery of the produced article to the testing team. Likewise, the test schedule will include a receiver milestone that represents the receipt of the production article. Key G/R milestones should be defined in the schedule basis document.

A horizontally traceable schedule dynamically reforecasts the date of a key milestone through network logic if activities related to accomplishing it are delayed longer than scheduled. For example, if the duration of a key milestone’s predecessor activity is greatly extended relative to available float, the date of the key milestone should slip. Activities whose durations are extended many days but have no effect on key milestones should be examined for unrealistic or dangling logic. Horizontal traceability is directly related to Best Practice 2 and is the result of a dynamic IMS whose activities are properly sequenced.