Modeling the Space Shuttle Liquid Hydrogen Subsystem

Abstract

Use of any trademarks in this report is not intended in any way to infringe on the rights of the trademark holder. Internal use. Permission to reproduce this document and to prepare derivative works from this document for internal use is granted, provided the copyright and "No Warranty" statements are included with all reproductions and derivative works.

Random search of AND-OR graphs representing finite-state models

“…We then put f = 0 into the queue at some random index, and in progressive iterations remove it and a = 1, neither of which will make it possible to reach any new nodes, so the search ends with the NAYO pictured on the right side ofFigure 3.9 (note: because the search makes random choices between contradictory options, this example result is just one of several possible results).Chapter Search of Example ModelsIn this chapter, the simple random search of Section 3.3 is modified to accommodate features of several example models. First, the search is extended to move across time (4.1), finding a series of internally consistent sets representing successive states of the program in execution.This version of the search is illustrated with an example model originally written in the SCR (software cost reduction) requirements specification language, the Space Shuttle Liquid Hydrogen Subsystem model from Atanacio[2]. Next the search and finite-state machine input language are modified to handle models of communications protocols, in which transitions may be triggered by messages passed from one finite-state machine to another (4.2).…”