Verification of Concurrent Systems : optimality, Scalability and Applicability

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Informática, leída el 14-10-2020Tanto el testing como la verificacion de sistemas concurrentes requieren explorar todos los posibles entrelazados no deterministas que la ejecucion concurrente puede tener, ya que cualquiera de estos entrelazados podra revelar un comportamiento erroneo del sistema. Esto introduce una explosion combinatoria en el numero de estados del programa que deben ser considerados, lo que frecuentemente lleva a un problema computacionalmente intratable. El objetivo de esta tesis es el desarrollo de tecnicas novedosas para el testing y la verificacion de programas concurrentes que permitan reducir esta explosion combinatoria...Both verification and testing of concurrent systems require exploring all possible non-deterministic interleavings that the concurrent execution may have, as any of the interleavings may reveal an erroneous behavior of the system. This introduces a combinatorial explosion on the number of program states that must be considered, what leads often to a computationally intractable problem. The overall goal of this thesis is to investigate novel techniques for testing and verification of concurrent programs that reduce this combinatorial explosion...Fac. de InformáticaTRUEunpu

Distributed Supervisory Control of Discrete-Event Systems with Communication Delay

This paper identifies a property of delay-robustness in distributed supervisory control of discrete-event systems (DES) with communication delays. In previous work a distributed supervisory control problem has been investigated on the assumption that inter-agent communications take place with negligible delay. From an applications viewpoint it is desirable to relax this constraint and identify communicating distributed controllers which are delay-robust, namely logically equivalent to their delay-free counterparts. For this we introduce inter-agent channels modeled as 2-state automata, compute the overall system behavior, and present an effective computational test for delay-robustness. From the test it typically results that the given delay-free distributed control is delay-robust with respect to certain communicated events, but not for all, thus distinguishing events which are not delay-critical from those that are. The approach is illustrated by a workcell model with three communicating agents

Robust decision-support tools for airport surface traffic

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 107-113).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Forecasts of departure demand are one of the driving inputs to tactical decision-support tools (DSTs) for airport surface traffic. While there are well-known results on average- or worst-case forecast uncertainty, it is the forecast errors which occur under best-case minimum-uncertainty conditions which constrain robust DST design and the achievable traffic benefits. These best-case errors have never previously been characterized. Several quantitative models and techniques for computing pushback forecasts are developed. These are tested against a dataset of 17,344 real-world airline ground operations covering 3 months of Lufthansa flights transiting Frankfurt International Airport. The Lufthansa dataset includes detailed timing information on all of the turn processes, including deboarding, catering, cleaning, fueling and boarding. The dataset is carefully filtered to obtain a sample of 3820 minimum-uncertainty ground events. The forecast models and techniques are tested against this sample, and it is observed that current pushback forecast errors (on the order of ±15min) cannot be reduced by a factor of more than 2 or 3. Furthermore, for each ground event, only 3 observations are necessary to achieve this best-case performance: the available ground-time between actual onblock and scheduled offblock; the time until deboarding begins; and the time until boarding ends. Any DST used in real-world operations must be robust to this "noise floor". To support the development of robust DSTs, a unified framework called ceno-scale modelling is developed.(cont.) This class of models encodes a wide range of observed delay mechanisms using multi-resource synchronization (MRS) feedback networks. A ceno-scale model instance is created for Newark International Airport, and the parameter sensitivity and model fidelity are tested against a detailed real-world dataset. Based on the validated model framework, several robust dual control strategies are proposed for airport surface traffic.by Francis R. Carr.Ph.D

Robust Decision-Support Tools for Airport Surface Traffic

Forecasts of departure demand are one of the driving inputs to tactical decision-support tools (DSTs) for airport surface traffic. While there are well-known results on average- or worst-case forecast uncertainty, it is the forecast errors which occur under best-case minimum-uncertainty conditions which constrain robust DST design and the achievable traffic benefits. These best-case errors have never previously been characterized. Several quantitative models and techniques for computing pushback forecasts are developed. These are tested against a dataset of 17,344 real-world airline ground operations covering 3 months of Lufthansa fights transiting Frankfurt International Airport. The Lufthansa dataset includes detailed timing information on all of the turn processes, including deboarding, catering, cleaning, fueling and boarding. The dataset is carefully filtered to obtain a sample of 3820 minimum-uncertainty ground events. The forecast models and techniques are tested against this sample, and it is observed that current pushback forecast errors (on the order of §15min) cannot be reduced by a factor of more than 2 or 3. Furthermore, for each ground event, only 3 observations are necessary to achieve this best-case performance: the available ground-time between actual onblock and scheduled offblock; the time until deboarding begins; and the time until boarding ends. Any DST used in real-world operations must be robust to this “noise floor". To support the development of robust DSTs, a unified framework called ceno-scale modeling is developed. This class of models encodes a wide range of observed delay mechanisms using multi-resource synchronization (MRS) feedback networks. A ceno-scale model instance is created for Newark International Airport, and the parameter sensitivity and model fidelity are tested against a detailed real-world dataset. Based on the validated model framework, several robust dual control strategies are proposed for airport surface traffic

Fault Injection and Monitoring Capability for a Fault-Tolerant Distributed Computation System

The Configurable Fault-Injection and Monitoring System (CFIMS) is intended for the experimental characterization of effects caused by a variety of adverse conditions on a distributed computation system running flight control applications. A product of research collaboration between NASA Langley Research Center and Old Dominion University, the CFIMS is the main research tool for generating actual fault response data with which to develop and validate analytical performance models and design methodologies for the mitigation of fault effects in distributed flight control systems. Rather than a fixed design solution, the CFIMS is a flexible system that enables the systematic exploration of the problem space and can be adapted to meet the evolving needs of the research. The CFIMS has the capabilities of system-under-test (SUT) functional stimulus generation, fault injection and state monitoring, all of which are supported by a configuration capability for setting up the system as desired for a particular experiment. This report summarizes the work accomplished so far in the development of the CFIMS concept and documents the first design realization