Purandar Bhaduri

Bio: Purandar Bhaduri is an academic researcher from Indian Institute of Technology Guwahati. The author has contributed to research in topics: Formal verification & Dynamic priority scheduling. The author has an hindex of 9, co-authored 40 publications receiving 328 citations. Previous affiliations of Purandar Bhaduri include Indian Institutes of Technology & Tata Consultancy Services.

Model Checking of Statechart Models: Survey and Research Directions

Abstract: We survey existing approaches to the formal verification of statecharts using model checking Although the semantics and subset of statecharts used in each approach varies considerably, along with the model checkers and their specification languages, most approaches rely on translating the hierarchical structure into the flat representation of the input language of the model checker This makes model checking difficult to scale to industrial models, as the state space grows exponentially with flattening We look at current approaches to model checking hierarchical structures and find that their semantics is significantly different from statecharts We propose to address the problem of state space explosion using a combination of techniques, which are proposed as directions for further research

Interface synthesis and protocol conversion

Abstract: Given deterministic interfaces P and Q, we investigate the problem of synthesising an interface R such that P composed with R refines Q. We show that a solution exists iff P and $$Q^\bot$$ are compatible, and the most general solution is given by $$(P \parallel Q^\bot)^\bot$$, where $$P^\bot$$ is the interface P with inputs and outputs interchanged. Remarkably, the result holds both for asynchronous and synchronous interfaces. We model interfaces using the interface automata formalism of de Alfaro and Henzinger. For the synchronous case, we give a new definition of synchronous interface automata based on Mealy machines and show that the result holds for a weak form of nondeterminism, called observable nondeterminism. We also characterise solutions to the synthesis problem in terms of winning input strategies in the automaton $$(P \otimes Q^\bot)^\bot$$, and the most general solution in terms of the most permissive winning strategy. We apply the solution to the synthesis of converters for mismatched protocols in both the asynchronous and synchronous domains. For the asynchronous case, this leads to automatic synthesis of converters for incompatible network protocols. In the synchronous case, we obtain automatic converters for mismatched intellectual property blocks in system-on-chip designs. The work reported here is based on earlier work on interface synthesis in Bhaduri (Third international symposium on automated technology for verification and analysis, ATVA 2005, pp 338–353, 2005) for the asynchronous case, and Bhaduri and Ramesh (Sixth international conference on application of concurrency to system design, ACSD 2006, pp 208–216) for the synchronous one.

Performance analysis of FlexRay-based systems using real-time calculus, revisited

Abstract: The FlexRay protocol [4] is likely to be the de facto standard for automotive communication systems. Hence, there is a need to provide hard performance guarantees on properties like worst case response times of messages, their buffer requirements, end-to-end latency (for example, from sensor to actuator), etc., for FlexRay based systems. The paper [11] provides an analysis for finding worst case response times of the messages transmitted on the FlexRay bus, but the analysis is done using ILP formulation and is thus computationally expensive. The paper [5] models the FlexRay in the analytic framework of Real-Time Calculus [12, 3] and is compositional as well as scalable. In this paper, we show that the analysis of [5] may lead to results that are over optimistic; in particular, we show that obtaining the "upper service curves" is not trivial and does not follow the reasoning of the "lower service curves" which the authors obtain. We also provide tighter "lower service curves" than that of [5]. Finally we show that our model allows the messages to be of variable size which is not the case with [5].

Modeling Fixed Priority Non-Preemptive Scheduling with Real-Time Calculus

Abstract: Modern real-time embedded systems are highly heterogeneous and distributed. As a result, compositional methods play an important role in the design and analysis of such complex systems. One such compositional analysis method is based on real-time calculus. In this paper, we present an analysis of fixed priority non-preemptive scheduling with the real-time calculus. Although fixed priority non-preemptive scheduling was modeled with the real-time calculus previously, we show that the model gives overly pessimistic results. We also compare our analysis with the existing holistic scheduling analysis through an example of a system using a controller area network (CAN) bus. The proposed method can be automated by incorporating it in the RTC toolbox.

Performance modeling and evaluation of IEEE 802.11 IBSS power save mode

Abstract: The IEEE 802.11 standard defines a power management algorithm for wireless LAN. In the power management for Independent Basic Service Set (IBSS), time is divided into Beacon Intervals (BIs) and each BI is divided into an Announcement Traffic Indication Message (ATIM) window and a data window. The stations that have successfully transmitted an ATIM frame within the ATIM window compete to transmit data frames in the rest of the BI. This paper analyzes the performance of the IEEE 802.11 Power Save Mode (PSM) in single hop ad hoc networks using a discrete-time Markov chain for a data frame transmission together with the corresponding ATIM frame transmission. The paper presents an analytical model to compute the throughput, average delay and power consumption in IEEE 802.11 IBSS in PSM under ideal channel and saturation conditions. The impact of network size on the throughput, delay and power consumption of the IEEE 802.11 DCF in Power Save Mode is also analyzed. This can be used to find an efficient scheme that can maximize the network throughput while saving power consumption for resource constrained ad hoc wireless networks. The analytical work is validated with simulation results obtained from Qualnet 5.0.1 network simulator.

Tools and Algorithms for the Construction and Analysis of Systems. Proc. TACAS 2009

Abstract: ing WS1S Systems to Verify Parameterized Networks . . . . . . . . . . . . 188 Kai Baukus, Saddek Bensalem, Yassine Lakhnech and Karsten Stahl FMona: A Tool for Expressing Validation Techniques over Infinite State Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 J.-P. Bodeveix and M. Filali Transitive Closures of Regular Relations for Verifying Infinite-State Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 Bengt Jonsson and Marcus Nilsson Diagnostic and Test Generation Using Static Analysis to Improve Automatic Test Generation . . . . . . . . . . . . . 235 Marius Bozga, Jean-Claude Fernandez and Lucian Ghirvu Efficient Diagnostic Generation for Boolean Equation Systems . . . . . . . . . . . . 251 Radu Mateescu Efficient Model-Checking Compositional State Space Generation with Partial Order Reductions for Asynchronous Communicating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Jean-Pierre Krimm and Laurent Mounier Checking for CFFD-Preorder with Tester Processes . . . . . . . . . . . . . . . . . . . . . . . 283 Juhana Helovuo and Antti Valmari Fair Bisimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Thomas A. Henzinger and Sriram K. Rajamani Integrating Low Level Symmetries into Reachability Analysis . . . . . . . . . . . . . 315 Karsten Schmidt Model-Checking Tools Model Checking Support for the ASM High-Level Language . . . . . . . . . . . . . . 331 Giuseppe Del Castillo and Kirsten Winter Table of

On the synthesis of discrete controllers for timed systems

Abstract: This paper presents algorithms for the automatic synthesis of real-time controllers by finding a winning strategy for certain games defined by the timed-automata of Alur and Dill. In such games, the outcome depends on the players' actions as well as on their timing. We believe that these results will pave the way for the application of program synthesis techniques to the construction of real-time embedded systems from their specifications.

A Basis for a Mathematical Theory of Computation

Abstract: Publisher Summary This chapter discusses the mathematical theory of computation. Computation essentially explores how machines can be made to carry out intellectual processes. Any intellectual process that can be carried out mechanically can be performed by a general purpose digital computer. There are three established directions of mathematical research that are relevant to the science of computation—namely, numerical analysis, theory of computability, and theory of finite automata. The chapter explores what practical results can be expected from a suitable mathematical theory. Further, the chapter presents several descriptive formalisms with a few examples of their use and theories that enable to prove the equivalence of computations expressed in these formalisms. A few mathematical results about the properties of the formalisms are also presented.

Contracts for System Design

Abstract: Recently, contract-based design has been proposed as an “orthogonal” approach that complements system design methodologies proposed so far to cope with the complexity of system design. Contract-based design provides a rigorous scaffolding for verification, analysis, abstraction/refinement, and even synthesis. A number of results have been obtained in this domain but a unified treatment of the topic that can help put contract-based design in perspective was missing. This monograph intends to provide such a treatment where contracts are precisely defined and characterized so that they can be used in design methodologies with no ambiguity. In particular, this monograph identifies the essence of complex system design using contracts through a mathematical “meta-theory”, where all the properties of the methodology are derived from a very abstract and generic notion of contract. We show that the meta-theory provides deep and illuminating links with existing contract and interface theories, as well as guidelines for designing new theories. Our study encompasses contracts for both software and systems, with emphasis on the latter. We illustrate the use of contracts with two examples: requirement engineering for a parking garage management, and the development of contracts for timing and scheduling in the context of the AUTOSAR methodology in use in the automotive sector.