Gurdip Singh’s research while affiliated with Syracuse University and other places

The development of cyber-physical systems is crucial for effective implementation of technologies for smart cities applications. Middleware algorithms have been studied extensively for traditional distributed systems. It is natural to leverage the existing work by extending these traditional algorithms to apply to cyber-physical systems. This paper presents a number of challenges that must be addressed in extending traditional algorithms for cyber-physical systems. First, since traditional algorithms view the underlying networked system as a graph, we present a model for cyber-physical systems that formalizes various aspects of both the cyber- and the physical system in terms of graphs. Second, we identify challenges to be addressed in extending traditional algorithms to CPS for the proposed graph-based models.

Cyber-Physical Systems (CPS) applications are being increasingly used to provide services in domains such as health-care, transportation, and energy. Providing such services may require interactions between applications, some of which may be unpredictable. Understanding and mitigating such interactions require that CPSs be designed as open and composable systems. Composition has been studied extensively in the literature. To complement this work, this paper studies composition of cyber algorithms with user behaviors in a CPS. Traditional middleware algorithms have been designed by abstracting away the underlying system and providing users with high-level APIs to interact with the physical system. In a CPS, however, users may interact directly with the physical system and may perform actions that are part of the services provided. We find that by accounting for user interactions and including them as part of the solution, one can design algorithms that are more efficient, predictable and resilient. To accomplish this, we propose a framework to model both the physical and the cyber systems. This framework allows specification of both physical algorithms and cyber algorithms. We discuss how such specifications can be composed to design middleware that leverages user actions. We show that such composite solutions preserve invariants of the component algorithms such as those related to functional properties and fault-tolerance. Our future work involves developing a comprehensive framework that uses compositionality is a key feature to address interdependent behavior of CPSs.

Distributed computing problems such as mutual exclusion have been studied extensively for traditional dis-tributed systems. In traditional systems, a strict layered approach is taken wherein a set of users (application processes) U1, . . . ,Un is layered on top of a mutual exclusion algorithm with processes P 1 , . . . , P n . User Ui interacts with process P i to request access to resources which are modeled as tokens, and users rely entirely on mutual exclusion algorithm to regulate access to the resources. In a cyber-physical system, users (physical entities) may themselves possess capabilities such as sensing, observing and mobility using which they may also attempt to locate physical resources such as wheelchairs. Thus, a mutual exclusion algorithm in a cyber-physical system must contend with the behavior of users. This paper proposes a graph-based model for cyber-physical systems which is used to describe mutual exclusion algorithm as well as user behavior. Based on this model, we present several solutions for the mutual exclusion problem. We have also conducted an extensive simulation study of our algorithms using OMNeT++ discrete event simulation system.