Radu Siminiceanu | National Institute of Aerospace (original) (raw)

Papers by Radu Siminiceanu

Integrated Formal …, Jan 1, 2012

The Plan Execution Interchange Language (PLEXIL) is an open source synchronous language developed... more The Plan Execution Interchange Language (PLEXIL) is an open source synchronous language developed by NASA for commanding and monitoring autonomous systems. This paper reports the development of the PLEXIL's Formal Interactive Verification Environment (PLEXIL5), a graphical interface to the formal executable semantics of PLEXIL. Among its main features, PLEXIL5 provides model checking of plans with support for formula editing and visualization of counterexamples, interactive simulation of plans at different granularity levels, and random initialization of external environment variables. The formal verification capabilities of PLEXIL5 are illustrated by means of a human-automation interaction model.

This paper presents a case study in modelling and verifying the Linux Virtual File System (VFS). ... more This paper presents a case study in modelling and verifying the Linux Virtual File System (VFS). Our work is set in the context of Hoare's verification grand challenge and, in particular, Joshi and Holzmann's mini-challenge to build a verifiable file system. The aim of the study is to assess the viability of retrospective verification of a VFS implementation using model-checking technology. We show how to extract an executable model of the Linux VFS implementation, validate the model by employing the simulation capabilities of SPIN, and analyse it for adherence to data integrity constraints and deadlock freedom using the SMART model checker.

Lecture Notes in Computer Science, 2012

A Survey of Applications, 2012

Science of Computer Programming, 2014

We present a case study of verifying the design of a commercial multi-threaded task server (MTTS)... more We present a case study of verifying the design of a commercial multi-threaded task server (MTTS), developed by the Novabase company, used for massively parallelising computational tasks. In a first stage, we employed the Plural tool, which is designed to perform lightweight verification of Java programs using a Data Flow Analysis (DFA) framework, to specify and verify the MTTS. We wrote the Plural specification for the MTTS based on the code developed by Novabase, its informal documentation, and our discussions with Novabase engineers, who validated our understanding of the MTTS application. The Plural specification language is based on typestates and access permissions. In a second stage, we developed the Pulse tool that enhances the analysis performed by Plural, and used the tool on the MTTS specifications. Pulse translates Plural specifications into an abstract state-machine model that captures the semantics of all the possible concurrent programs implementing the given specifications, and uses the evmdd-smc symbolic model-checker to verify the machine model. The experimental results on the MTTS specification show that the exhaustive model-checking approach scales reasonably well and is efficient at finding errors in specifications that were not previously detected with the Data Flow Analysis (DFA) capabilities of Plural.

The Saturation algorithm for symbolic state-space generation is a recent advance in exhaustive ve... more The Saturation algorithm for symbolic state-space generation is a recent advance in exhaustive verification of complex systems, in particular globally-asynchronous/ locally-synchronous systems. The distributed version of Saturation uses the overall memory available on a network of workstations (NOW) to efficiently spread the memory load during its highly irregular exploration. A crucial factor in limiting the memory consumption in symbolic state-space generation is the ability to perform garbage collection to free up the memory occupied by dead nodes. However, garbage collection over a NOW requires a nontrivial communication overhead. In addition, operation cache policies become critical while analyzing large-scale systems using a symbolic approach. In this paper, we develop a garbage collection scheme and several operation cache policies to help the analysis of complex systems. Experiments show that our schemes improve the performance of the original distributed implementation, S m A r T N ow , in terms of both time and memory efficiency.

We describe the main features of S m A r T, a software package providing a seamless environment f... more We describe the main features of S m A r T, a software package providing a seamless environment for the logic and probabilistic analysis of complex systems. S m A r T can combine different formalisms in the same modeling study. For the analysis of logical behavior, both explicit and symbolic state-space generation techniques, as well as symbolic CTL model-checking algorithms, are available. For the study of stochastic and timing behavior, both sparse-storage and Kronecker numerical solution approaches are available when the underlying process is a Markov chain. In addition, discrete-event simulation is always applicable regardless of the stochastic nature of the process, but certain classes of non-Markov models can still be solved numerically. Finally, since S m A r T targets both the classroom and realistic industrial settings as a learning, research, and application tool, it is written in a modular way that allows for easy integration of new formalisms and solution algorithms.

The Saturation algorithm for symbolic state-space generation, has been a recent break-through in ... more The Saturation algorithm for symbolic state-space generation, has been a recent break-through in the exhaustive verification of complex systems, in particular globally-asyn-chronous/locally-synchronous systems. The algorithm uses a very compact Multiway Decision Diagram (MDD) encoding for states and the fastest symbolic exploration algo-rithm to date. The distributed version of Saturation uses the overall memory available on a network of workstations (NOW) to efficiently spread the memory load during the highly irregular exploration. A crucial factor in limiting the memory consumption during the symbolic state-space generation is the ability to perform garbage collection to free up the memory occupied by dead nodes. However, garbage collection over a NOW requires a nontrivial communication overhead. In addition, operation cache poli-cies become critical while analyzing large-scale systems using the symbolic approach. In this technical report, we develop a garbage collection scheme a...

Embedded distributed systems have become an integral part of many safety-critical applications. T... more Embedded distributed systems have become an integral part of many safety-critical applications. There have been many attempts to solve the self-stabilization problem of clocks across a distributed system. An analysis of one such protocol called the Byzantine Self-Stabilizing Pulse Synchronization (BSS-Pulse-Synch) protocol from a paper entitled "Linear Time Byzantine Self-Stabilizing Clock Synchronization" by Daliot et al [Daliot 03] is presented in this report. This report also includes a discussion of the complexity and pitfalls of designing self-stabilizing protocols and provides counterexamples for the claims of the above protocol.

Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. ... more Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA’s scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA’s institutional mechanism for disseminating the results of its research and development activities. These results are published by

Lecture Notes in Computer Science, 2003

Lecture Notes in Computer Science, 2001

Lecture Notes in Computer Science, 2002

We present a new method for the symbolic construction of shortest paths in reachability graphs. O... more We present a new method for the symbolic construction of shortest paths in reachability graphs. Our algorithm relies on a variant of edge-valued decision diagrams that supports efficient fixed-point iterations for the joint computation of both the reachable states and their distance from the initial states. Once the distance function is known, a shortest path from an initial state to a state satisfying a given condition can be easily obtained. Using a few representative examples, we show how our algorithm is vastly superior, in terms of both memory and space, to alternative approaches that compute the same information, such as ordinary or algebraic decision diagrams.

Lecture Notes in Computer Science, 2000

Many state-of-the-art techniques for the veri cation of today's complex embedded systems rely on ... more Many state-of-the-art techniques for the veri cation of today's complex embedded systems rely on the analysis of their reachable state spaces. In this paper, we develop a new algorithm for the symbolic generation of the state space of asynchronous system models, such as Petri nets. The algorithm is based on previous work that employs Multi-valued Decision Diagrams (MDDs) for e ciently storing sets of reachable states. In contrast to related approaches, however, it fully exploits event locality which is a fundamental semantic property of asynchronous systems. Additionally, the algorithm supports intelligent cache management and achieves faster convergence via advanced iteration control. It is implemented in the tool SMART, and run-time results for several examples taken from the Petri net literature show that the algorithm performs about one order of magnitude faster than the best existing state-space generators.

Lecture Notes in Computer Science, 2006

We investigate a new class of metrics to find good variable orders for decision diagrams in symbo... more We investigate a new class of metrics to find good variable orders for decision diagrams in symbolic state-space generation. Most of the previous work on static ordering is centered around the concept of minimum variable span, which can also be found in the literature under several other names. We use a similar concept, but applied to event span, and generalize it to a family of metrics parameterized by a moment, where the metric of moment 0 is the combined event span. Finding a good variable order is then reduced to optimizing one of these metrics, and we design extensive experiments to evaluate them. First, we investigate how the actual optimal order performs in state-space generation, when it can be computed by evaluating all possible permutations. Then, we study the performance of these metrics on selected models and compare their impact on two different state-space generation algorithms: classic breadth-first and our own saturation strategy. We conclude that the new metric of moment 1 is the best choice. In particular, the saturation algorithm seems to benefit the most from using it, as it achieves the better performance in nearly 80% of the cases. ⋆