Lee, Insup
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Publication Generic Infusion Pump Hazard Analysis and Safety Requirements Version 1.0(2009-02-06) Arney, David E.; Jetley, Raoul; Lee, Insup; Jones, Paul; Sokolsky, Oleg; Ray, Arnab; Zhang, YiThe Generic Infusion Pump (or GIP) project is an effort to make generic formal models of infusion pump systems. Our process of building these formal models started with requirements elicitation and hazard analysis. This document contains the informal requirements and hazard analysis used to create a generic pump model. We plan to use these models and properties to generate tests which can be used for conformance testing infusion pump implementations. Our future work will focus on extending these pump models with additional safety requirements and exploring the use of test generation for conformance testing real pump implementations.Publication Communicating Shared Resources: A Paradigm for Integrating Real-Time Specification and Implementation(1991-03-15) Lee, Insup; Davidson, Susan B; Gerber, RichardThe timed behavior of distributed real-time systems can be specified using a formalism called Communicating Shared Resources, or CSR. The underlying computation model of CSR is resource-based in which multiple resources execute synchronously, while processes assigned to the same resource are interleaved according to their priorities. CSR bridges the gap between an abstract computation model and implementation environments, but is too complex to be treated as a process algebra. We therefore give a calculus for CSR (CCSR), that provides the ability to perform equivalence proofs by syntactic manipulation. We illustrate how a CSR specification can be translated into the CCSR formalism using a periodic timed producer-consumer example, and how a translated CSR specification can be shown correct using syntactic manipulations.Publication Rationale and Architecture Principles for Medical Application Platforms(2012-04-01) Hatcliff, John; King, Andrew; Lee, Insup; MacDonald, Alasdair; Fernando, Anura; Robkin, Michael; Vasserman, Eugene; Weininger, Sandy; Goldman, Julian M.The concept of “system of systems” architecture is increasingly prevalent in many critical domains. Such systems allow information to be pulled from a variety of sources, analyzed to discover correlations and trends, stored to enable realtime and post-hoc assessment, mined to better inform decisionmaking, and leveraged to automate control of system units. In contrast, medical devices typically have been developed as monolithic stand-alone units. However, a vision is emerging of a notion of a medical application platform (MAP) that would provide device and health information systems (HIS) interoperability, safety critical network middleware, and an execution environment for clinical applications (“apps”) that offer numerous advantages for safety and effectiveness in health care delivery. In this paper, we present the clinical safety/effectiveness and economic motivations for MAPs, and describe key characteristics of MAPs that are guiding the search for appropriate technology, regulatory, and ecosystem solutions. We give an overview of the Integrated Clinical Environment (ICE) – one particular achitecture for MAPs, and the Medical Device Coordination Framework – a prototype implementation of the ICE architecture.Publication R-Charon, a Modeling Language for Reconfigurable Hybrid Systems(2006-03-29) Sokolsky, Oleg; Pappas, George; Kratz, Fabian; Lee, InsupThis paper describes the modeling language as an extension for architectural reconfiguration to the existing distributed hybrid system modeling language Charon. The target application domain of R-Charon includes but is not limited to modular reconfigurable robots and large-scale transportation systems. While largely leaving the Charon syntax and semantics intact, R-Charon allows dynamic creation and destruction of components (agents) as well as of links (references) between the agents. As such, R-Charon is the first formal, hybrid automata based modeling language which also addresses dynamic reconfiguration. We develop and present the syntax and operational semantics for R-Charon on three levels: behavior (modes), structure (agents) and configuration (system).Publication QuanTM: A Quantitative Trust Management System(2009-03-01) West, Andrew G; Aviv, Adam J; Chang, Jian; Prabhu, Vinayak S; Blaze, Matthew A; Kannan, Sampath; Lee, Insup; Smith, Jonathan M; Sokolsky, OlegQuantitative Trust Management (QTM) provides a dynamic interpretation of authorization policies for access control decisions based on upon evolving reputations of the entities involved. QuanTM, a QTM system, selectively combines elements from trust management and reputation management to create a novel method for policy evaluation. Trust management, while effective in managing access with delegated credentials (as in PolicyMaker and KeyNote), needs greater flexibility in handling situations of partial trust. Reputation management provides a means to quantify trust, but lacks delegation and policy enforcement. This paper reports on QuanTM’s design decisions and novel policy evaluation procedure. A representation of quantified trust relationships, the trust dependency graph, and a sample QuanTM application specific to the KeyNote trust management language, are also proposed.Publication A Compositional Framework for Avionics (ARINC-653) Systems(2009-01-01) Lee, Insup; Easwaran, Arvind; Sokolsky, Oleg; Vestal, SteveCyber-physical systems (CPSs) are becoming all-pervasive, and due to increasing complexity they are designed using component-based approaches. Temporal constraints of such complex CPSs can then be modeled using hierarchical scheduling frameworks. In this paper, we consider one such avionics CPS described by ARINC specification 653-2. The real-time workload in this system comprises of partitions, where each partition consists of one or more processes. Processes incur blocking and preemption overheads, and can communicate with other processes in the system. In this work, we develop techniques for automated scheduling of such partitions. At present, system designers manually schedule partitions based on interactions they have with application vendors. This approach is not only time consuming, but can also result in under utilization of resources. Hence, in this work we propose compositional analysis based scheduling techniques for partitions.Publication Process Algebraic Modeling and Analysis of Power-Aware Real-Time Systems(2002-08-01) Lee, Insup; Sokolsky, Oleg; Philippou, AnnaThe 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 Schedulability Analysis of AADL models(2006-04-29) Sokolsky, Oleg; Lee, Insup; Clark, DuncanThe 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 Video Quality Driven Buffer Sizing via Frame Drops(2011-08-01) Gangadharan, Deepak; Phan, Linh T.X.; Chakraborty, Samarjit; Zimmermann, Roger; Lee, InsupWe study the impact of video frame drops in buffer constrained multiprocessor system-on-chip (MPSoC) platforms. Since on-chip buffer memory occupies a significant amount of silicon area, accurate buffer sizing has attracted a lot of research interest lately. However, all previous work studied this problem with the underlying assumption that no video frame drops can be tolerated. In reality, multimedia applications can often tolerate some frame drops without significantly deteriorating their output quality. Although system simulations can be used to perform video quality driven buffer sizing, they are time consuming. In this paper, we first demonstrate a dual-buffer management scheme to drop only the less significant frames. Based on this scheme, we then propose a formal framework to evaluate the buffer size vs. video quality trade-offs, which in turn will help a system designer to perform quality driven buffer sizing. In particular, we mathematically characterize the maximum numbers of frame drops for various buffer sizes and evaluate how they affect the worst-case PSNR value of the decoded video. We evaluate our proposed framework with an MPEG-2 decoder and compare the obtained results with that of a cycle-accurate simulator. Our evaluations show that for an acceptable quality of 30 dB, it is possible to reduce the buffer size by upto 28.6% which amounts to 25.88 megabits.Publication Towards Synthesis of Platform-Aware Attack-Resilient Control Systems: Extended Abstract(2013-04-09) Pajic, Miroslav; Bezzo, Nicola; Weimer, James; Alur, Rajeev; Mangharam, Rahul; Michael, Nathan; Pappas, George J; Sokolsky, Oleg; Tabuada, Paulo; Weirich, Stephanie; Lee, Insup