Gossiping Components for Cyber-Physical Systems

Abstract

Abstract. Developing software for dynamic cyber-physical systems (CPS) is a complex task. One has to deal with the dynamicity and unreliability of the physical environment where the software resides in, while, at the same time, provide sufficient levels of dependability and scalability. Although emerging software engineering abstractions, such as dynamic ad-hoc component ensembles, provide a convenient way to structure software for dynamic CPS, they need to be mapped to robust decentralized execution schemes in real-life settings. A particular challenge in this context is the robust distributed data dissemination in dynamic networks. Gossip-based communication stands as a promising solution to this challenge. We argue, that exploitation of application-specific information, software architecture in particular, has a large potential for improving the robustness and performance of gossip-based communication. This paper proposes a synergy between high-level architectural models and low-level communication models to effectively enable application-specific gossiping in component-based systems. The synergy is exemplified on the DEECo component model which is tailored to the needs and specifics of CPS, and evaluated on an emergency coordination case study with realistic network configurations.

Adaptive Exchange of Distributed Partial Models@run.time for Highly Dynamic Systems

“…In particular, every node in a DEECo application periodically and proactively gossips both its own and the knowledge of other nodes that it knows of with all other nodes 1 [23]. In our example, this means that all the knowledge of the Room is passed to the Robot, and vice versa.…”

“…In DEECo, the knowledge of every component is proactively shared among all components and only used in components of the same ensemble (the ensemble membership condition is evaluated locally in each component) [23]. SeSaMe handles knowledge distribution through dynamic roles that restrict the amount of knowledge to be shared among interacting components.…”

Employing Domain Knowledge for Optimizing Component Communication

“…Its state is captured by knowledge (a set of attributes -lines [7][8][9][10][11][12][13][14] and operational functionality by processes (lines [15][16][17][18][19][20]. Every component features a number of roles, i.e., sets of knowledge fields (lines [1][2][3][4]6), which provide contract between the component and ensembles. Processes are executed by the runtime periodically or in a triggered manner.…”

“…Tailored for development of sCPS, the DEECo component model allows designing a system at the architecture level without considering aspects related to its actual deployment -component In this section, we present how this can be achieved in DEECo by employing the concept of communication boundary [3], and, as a key contribution, the novel idea of communication groups.…”

“…The communication protocol in jDEECo is based on bounded gossiping [3], where components' knowledge rebroadcasting is limited by communication boundaries articulated in ensemble specifications. A communication boundary is employed by a node for deciding whether or not to rebroadcast the component knowledge heard from other nodes.…”