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Graph models for reachability analysis of concurrent programs
Reachability analysis is an attractive technique for analysis of concurrent programs because it is simple and relatively straightforward to automate, and can be used in conjunction with model-checking procedures to check for application-specific as well as general properties. Several techniques have been proposed differing mainly on the model used; some of these propose the use of flowgraph based models, some others of Petri nets.This paper addresses the question: What essential difference does it make, if any, what sort of finite-state model we extract from program texts for purposes of reachability analysis? How do they differ in expressive power, decision power, or accuracy? Since each is intended to model synchronization structure while abstracting away other features, one would expect them to be roughly equivalent.We confirm that there is no essential semantic difference between the most well known models proposed in the literature by providing algorithms for translation among these models. This implies that the choice of model rests on other factors, including convenience and efficiency.Since combinatorial explosion is the primary impediment to application of reachability analysis, a particular concern in choosing a model is facilitating divide-and-conquer analysis of large programs. Recently, much interest in finite-state verification systems has centered on algebraic theories of concurrency. Yeh and Young have exploited algebraic structure to decompose reachability analysis based on a flowgraph model. The semantic equivalence of graph and Petri net based models suggests that one ought to be able to apply a similar strategy for decomposing Petri nets. We show this is indeed possible through application of category theory
Design of an integrated airframe/propulsion control system architecture
The design of an integrated airframe/propulsion control system architecture is described. The design is based on a prevalidation methodology that uses both reliability and performance. A detailed account is given for the testing associated with a subset of the architecture and concludes with general observations of applying the methodology to the architecture
On the engineering of crucial software
The various aspects of the conventional software development cycle are examined. This cycle was the basis of the augmented approach contained in the original grant proposal. This cycle was found inadequate for crucial software development, and the justification for this opinion is presented. Several possible enhancements to the conventional software cycle are discussed. Software fault tolerance, a possible enhancement of major importance, is discussed separately. Formal verification using mathematical proof is considered. Automatic programming is a radical alternative to the conventional cycle and is discussed. Recommendations for a comprehensive approach are presented, and various experiments which could be conducted in AIRLAB are described
An Agent-Based Simulation API for Speculative PDES Runtime Environments
Agent-Based Modeling and Simulation (ABMS) is an effective paradigm to model systems exhibiting complex interactions, also with the goal of studying the emergent behavior of these systems. While ABMS has been effectively used in many disciplines, many successful models are still run only sequentially. Relying on simple and easy-to-use languages such as NetLogo limits the possibility to benefit from more effective runtime paradigms, such as speculative Parallel Discrete Event Simulation (PDES). In this paper, we discuss a semantically-rich API allowing to implement Agent-Based Models in a simple and effective way. We also describe the critical points which should be taken into account to implement this API in a speculative PDES environment, to scale up simulations on distributed massively-parallel clusters. We present an experimental assessment showing how our proposal allows to implement complicated interactions with a reduced complexity, while delivering a non-negligible performance increase
NASA Formal Methods Workshop, 1990
The workshop brought together researchers involved in the NASA formal methods research effort for detailed technical interchange and provided a mechanism for interaction with representatives from the FAA and the aerospace industry. The workshop also included speakers from industry to debrief the formal methods researchers on the current state of practice in flight critical system design, verification, and certification. The goals were: define and characterize the verification problem for ultra-reliable life critical flight control systems and the current state of practice in industry today; determine the proper role of formal methods in addressing these problems, and assess the state of the art and recent progress toward applying formal methods to this area
Optimal classical simulation of state-independent quantum contextuality
Simulating quantum contextuality with classical systems requires memory. A
fundamental yet open question is what is the minimum memory needed and,
therefore, the precise sense in which quantum systems outperform classical
ones. Here, we make rigorous the notion of classically simulating quantum
state-independent contextuality (QSIC) in the case of a single quantum system
submitted to an infinite sequence of measurements randomly chosen from a finite
QSIC set. We obtain the minimum memory needed to simulate arbitrary QSIC sets
via classical systems under the assumption that the simulation should not
contain any oracular information. In particular, we show that, while
classically simulating two qubits tested with the Peres-Mermin set requires
bits, simulating a single qutrit tested with the
Yu-Oh set requires, at least, bits.Comment: 7 pages, 4 figure
Advanced flight control system study
A fly by wire flight control system architecture designed for high reliability includes spare sensor and computer elements to permit safe dispatch with failed elements, thereby reducing unscheduled maintenance. A methodology capable of demonstrating that the architecture does achieve the predicted performance characteristics consists of a hierarchy of activities ranging from analytical calculations of system reliability and formal methods of software verification to iron bird testing followed by flight evaluation. Interfacing this architecture to the Lockheed S-3A aircraft for flight test is discussed. This testbed vehicle can be expanded to support flight experiments in advanced aerodynamics, electromechanical actuators, secondary power systems, flight management, new displays, and air traffic control concepts
Study of fault-tolerant software technology
Presented is an overview of the current state of the art of fault-tolerant software and an analysis of quantitative techniques and models developed to assess its impact. It examines research efforts as well as experience gained from commercial application of these techniques. The paper also addresses the computer architecture and design implications on hardware, operating systems and programming languages (including Ada) of using fault-tolerant software in real-time aerospace applications. It concludes that fault-tolerant software has progressed beyond the pure research state. The paper also finds that, although not perfectly matched, newer architectural and language capabilities provide many of the notations and functions needed to effectively and efficiently implement software fault-tolerance
Towards a verified transformation from AADL to the formal component-based language FIACRE
International audienceDuring the last decade, aadlâ
is an emerging architecture description languages addressing the modeling of embedded systems. Several research projects have shown that aadlâ
concepts are well suited to the design of embedded systems. Moreover, aadlâ
has a precise execution model which has proved to be one key feature for effective early analysis. In this paper, we are concerned with the foundational aspects of the verification support for aadl. More precisely, we propose a verification toolchain for aadlâ
models through its transformation to the Fiacreâ
language which is the pivot verification language of the TOPCASED project: high level models can be transformed to Fiacreâ
models and then model-checked. Then, we investigate how to prove the correctness of the transformation from AADL into Fiacreâ
and present related elementary ingredients: the semantics of aadlâ
and Fiacreâ
subsets expressed in a common framework, namely timed transition systems. We also briefly discuss experimental validation of the work
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