Temporal Reasoning for Airlift Scheduling Analysis

Deliberate planning for airlift operations consists of an iterated cycle of resource allocation, simulation, and analysis. The process can be extremely time-consuming for large plans and the final schedule is uncomfortably sensitive to allocation decisions made early in the cycle. These problems can be alleviated by inserting an analysis phase prior to simulation, thereby saving simulation cycles and providing the planner with early feedback about the implications of high-level resource allocation decisions. One useful form of feedback for transportation schedules is an analysis of the temporal constraints among events in the plan. Temporal reasoning provides a general mechanism integrating various types of temporal constraints on airlift events to provide time bounds on execution of the complete plan. For this purpose we developed a general temporal constraint reasoner and a set of mechanisms for deriving temporal information from airlift requirements and partial schedule specifications. Physical limitations of the aircraft and operating facilities as well as the availability of cargo all provide constraints on when certain events may occur. Constraints include the time required to fly from one location to another or the time spent waiting for an aircraft to be loaded. Comparing cargo requirements with airlift capacity over time provides additional constraints. By considering these constraints and their interactions, the planner is in a better position to assess the impact of high-level planning decisions.
Presented at the IEEE 1990 National Aerospace and Electronics Conference (NAECON 1990), held in Dayton, Ohio on 21-25 May 1990.