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Author: Sokolsky, Oleg ×

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  • Publication
    Architecture-Centric Software Development for Cyber-Physical Systems
    (2014-10-01) Sokolsky, Oleg; Pajic, Miroslav; Bezzo, Nicola; Lee, Insup
    We discuss the problem of high-assurance development of cyber-physical systems. Specifically, we concentrate on the interaction between the development of the control system layer and platform-specific software engineering for system components. We argue that an architecture-centric approach allows us to streamline the development and increase the level of assurance for the resulting system. The case study of an unmanned ground vehicle illustrates the approach.
  • Publication
    A Retrospective Look at the Monitoring and Checking (MaC) Framework
    (2019-10-01) Kannan, Sampath; Kim, Moonzoo; Lee, Insup; Sokolsky, Oleg; Viswanathan, Mahesh
    The Monitoring and Checking (MaC) project gave rise to a framework for runtime monitoring with respect to formally specified properties, which later came to be known as runtime verification. The project also built a pioneering runtime verification tool, Java-MaC, that was an instantiation of the approach to check properties of Java programs. In this retrospective, we discuss decisions made in the design of the framework and summarize lessons learned in the course of the project.
  • Publication
    Schedulability Analysis of AADL models
    (2006-04-29) Sokolsky, Oleg; Lee, Insup; Clark, Duncan
    The paper discusses the use of formal methods for the analysis of architectural models expressed in the modeling language AADL. AADL describes the system as a collection of interacting components. The AADL standard prescribes semantics for the thread components and rules of interaction between threads and other components in the system. We present a semantics-preserving translation of AADL models into the real-time process algebra ACSR, allowing us to perform schedulability analysis of AADL models.
  • Publication
    Process Algebraic Modeling and Analysis of Power-Aware Real-Time Systems
    (2002-08-01) Lee, Insup; Philippou, Anna; Sokolsky, Oleg
    The paper describes a unified formal framework for designing and reasoning about power-constrained, real-time systems. The framework is based on process algebra, a formalism which has been developed to describe and analyze communicating, concurrent systems. The proposed extension allows the modeling of probabilistic resource failures, priorities of resource usages, and power consumption by resources within the same formalism. Thus, it is possible to evaluate alternative power-consumption behaviors and tradeoffs under different real-time schedulers, resource limitations, resource failure probabilities, etc. This paper describes the modeling and analysis techniques, and illustrates them with examples, including a dynamic voltage-scaling algorithm.
  • Publication
    Visual Programming for Modeling and Simulation of Biomolecular Regulatory Networks
    (2002-12-18) Alur, Rajeev; Belta, Calin; Ivancic, Franjo; Kumar, R. Vijay; Rubin, Harvey; Schug, Jonathan; Sokolsky, Oleg; Webb, Jonathan
    In this paper we introduce our new tool BIOSKETCHPAD that allows visual programming and modeling of biological regulatory networks. The tool allows biologists to create dynamic models of networks using a menu of icons, arrows, and pop-up menus, and translates the input model into CHARON, a modeling language for modular design of interacting multi-agent hybrid systems. Hybrid systems are systems that are characterized by continuous as well as discrete dynamics. Once a CHARON model of the underlying system is generated, we are able to exploit the various analysis capabilities of the CHARON toolkit, including simulation and reachability analysis. We illustrate the advantages of this approach using a case study concerning the regulation of bioluminescence in a marine bacterium.
  • Publication
    Resilient Parameter-Invariant Control With Application to Vehicle Cruise Control
    (2013-03-20) Weimer, James; Bezzo, Nicola; Pajic, Miroslav; Pappas, George J.; Sokolsky, Oleg; Lee, Insup
    This work addresses the general problem of resilient control of unknown stochastic linear time-invariant (LTI) systems in the presence of sensor attacks. Motivated by a vehicle cruise control application, this work considers a first order system with multiple measurements, of which a bounded subset may be corrupted. A frequency-domain-designed resilient parameter-invariant controller is introduced that simultaneously minimizes the effect of corrupted sensors, while maintaining a desired closed-loop performance, invariant to unknown model parameters. Simulated results illustrate that the resilient parameter-invariant controller is capable of stabilizing unknown state disturbances and can perform state trajectory tracking.
  • Publication
    Statistical Runtime Checking of Probabilistic Properties
    (2007-03-13) Sammapun, Usa; Lee, Insup; Sokolsky, Oleg; Regehr, John
    Probabilistic correctness is an important aspect of reliable systems. A soft real-time system, for instance, may be designed to tolerate some degree of deadline misses under a threshold. Since probabilistic systems may behave differently from their probabilistic models depending on their current environments, checking the systems at runtime can provide another level of assurance for their probabilistic correctness. This paper presents a statistical runtime verification for probabilistic properties using statistical analysis. However, while this statistical analysis collects a number of execution paths as samples to check probabilistic properties within some certain error bounds, runtime verification can only produce one single sample. This paper provides a technique to produce such a number of samples and applies this methodology to check probabilistic properties in wireless sensor network applications.
  • Publication
    A Safety-Assured Development Approach for Real-Time Software
    (2010-08-23) Jee, Eunkyoung; Wang, Shaohui; Kim, Jeong Ki; Lee, Jaewoo; Sokolsky, Oleg; Lee, Insup
    Guaranteeing timing properties is an important issue as we develop safety-critical real-time systems such as cardiac pacemakers. We present a safety assured development approach of real-time software using a pacemaker as our case study. Following the model-driven development techniques, measurement-based timing analysis is used to guarantee timing properties in implementation as well as in the formal model. Formal specification with timed automata is checked with respect to timing properties by model checking technique and is transformed into implementation systematically. When timing properties may be violated in the implementation due to timing delay, it is suggested to measure the time deviation and reflect it to the code explicitly by modifying guards. The model is altered according to the modifications in the code. These changes of the code and the model are considered safe if all the properties are still satisfied by the modified model in re-performed model hecking. We demonstrate how the suggested approach can be applied to single-threaded and multi-threaded versions of implementation. This approach can provide developers with a useful time-guaranteeing technique applicable to several code generation schemes without imposing many restrictions.
  • Publication
    Towards Assurance for Plug & Play Medical Systems
    (2015-09-01) King, Andrew L.; Feng, Lu; Procter, Sam; Chen, Sanjian; Sokolsky, Oleg; Hatcliff, John; Lee, Insup
    Traditional safety-critical systems are designed and integrated by a systems integrator. The system integrator can asses the safety of the completed system before it is deployed. In medicine, there is a desire to transition from the traditional approach to a new model wherein a user can combine various devices post-hoc to create a new composite system that addresses a specific clinical scenario. Ensuring the safety of these systems is challenging: Safety is a property of systems that arises from the interaction of system components and it’s not possible to asses overall system safety by assessing a single component in isolation. It is unlikely that end-users will have the engineering expertise or resources to perform safety assessments each time they create a new composite system. In this paper we describe a platform-oriented approach to providing assurance for plug & play medical systems as well as an associated assurance argument pattern.
  • Publication
    RT-MaC: Runtime Monitoring and Checking of Quantitative and Probabilistic Properties
    (2005-08-17) Sammapun, Usa; Lee, Insup; Sokolsky, Oleg
    Correctness of a real-time system depends on its computation as well as its timeliness and its reliability. In recent years, researches have focused on verifying correctness of a real-time system during runtime by monitoring its execution and checking it against its formal specifications. Such verification method is called Runtime Verification. Most existing runtime verification tools verify computation correctness using qualitative property specifications but do not verify timeliness nor reliability correctness. In this paper, we investigate the verification on timeliness and reliability correctness by offering quantitative and probabilistic property specifications and implementing efficient verifiers.