Time Management Situation Assessment (tmsa)*

TMSA is a concept prototype developed to support NASA Test Directors (NTDs) in schedule execution monitoring during the later stages of a Shuttle countdown. The program detects qualitative and quantitative constraint violations in near real-time. The next version will support incremental rescheduling, and reason over a substantially larger number of scheduled events. INTRODUCTION The Time Management Situation Assessment (TMSA) program is a prototype developed assist NASA Test Directors (NTDs) manage the later stages of a Shuttle countdown. The NTDs are primarily concerned with the orderly and timely execution of the countdown process. The cognitive model they reason with is a relatively high-level one which includes a nominal (planned) model of the countdown and set of qualitative and quantitative constraints that define such a countdown by specifying temporal duration and ordinal relationships between countdown events. Constraints vary both in their specificity (e.g. < is more explicit, <= is less explicit) and in their necessity (i.e. from critical more necessary to desirable less necessary). From the perspective of knowledge engineering for TMSA, what is not included in the NTDs’ view is as important as what is included. The details of a subsystem or procedural failure, and what is required to correct or bypass it are not, for the purposes of TMSA, a part of the NTDs’ view of the *This work is a portion of the technical support provided to the Artificial Intelligence Section, Design Engineering Directorate, by Boeing Aerospace Operations under the Engineering Support Contract at Kennedy Space Center. Arthur E. Belier is the NASA Technical Contact. countdown situation. Even in an anomalous situation the NTDs’ focus remains on the temporal duration and ordinal unfolding of the countdown. When an anomaly occurs the NTDs participate in the anomaly response, primarily, for the purpose of determining the impact the anomaly will have on the temporal and ordinal aspects of the countdown. The NTDs monitor the current countdown and assess its compliance with their nominal countdown model. When there is a need for a deviation, they consider alternative revisions of the current countdown and assess the legality and desirability of the revised countdown with regard to the constraints. The countdown schedule may be revised by reordering events and/or adjusting the durations of intervals between events. The existing prototype monitors launch processing during the later stages of the countdown. It detects deviations from a nominal countdown by detecting temporal and prerequisite constraint violations. It then identifies the violated constraint(s). The system is initialized and operates with both qualitative and quantitative constraints on the order of events and intervals, and the duration of intervals. The prototype is implemented in Smalltalk and runs on a 25mhz 486, under MS DOS. It appears that a C++ version of the program will be able to handle a schedule containing 200-300 events with response times of < 1.5 seconds for each assimilation input (i.e. relation vector refinement). SALIENT CHARACTERISTICS OF THE SITUATION In formulating our approach to this scheduling task we found the following characteristics of the situation to be especially important. 145 From: AAAI Technical Report SS-92-01. Compilation copyright © 1992, AAAI (www.aaai.org). All rights reserved.