Timed Actors and Their Formal Verification

In this paper we review the actor-based language, Timed Rebeca, with a focus on its formal semantics and formal verification techniques. Timed Rebeca can be used to model systems consisting of encapsulated components which communicate by asynchronous message passing. Messages are put in the message buffer of the receiver actor and can be seen as events. Components react to these messages/events and execute the corresponding message/event handler. Real-time features, like computation delay, network delay and periodic behavior, can be modeled in the language. We explain how both Floating-Time Transition System (FTTS) and common Timed Transition System (TTS) can be used as the semantics of such models and the basis for model checking. We use FTTS when we are interested in event-based properties, and it helps in state space reduction. For checking the properties based on the value of variables at certain point in time, we use the TTS semantics. The model checking toolset supports schedulability analysis, deadlock and queue-overflow check, and assertion based verification of Timed Rebeca models. TCTL model checking based on TTS is also possible but is not integrated in the tool.Comment: In Proceedings EXPRESS/SOS2023, arXiv:2309.0578

Functional and Performance Analysis of Network-on-Chips Using Actor-based Modeling and Formal Verification

Network on Chip (NoC) has emerged as a promising architecture paradigmfor todays many-core systems. As complexity grows in NoCs, functional verificationand performance prediction in the early stages of the design process are suggestedas ways to reduce the fabrication cost. Formal methods have gained moreattention as alternative ways for analyzing NoC designs. In this paper we propose amethod to model different characteristics of the system, and also verify various functionaland performance properties by generating the full state space of the model fordifferent scenarios. We present a formal model for two-dimensional mesh GloballyAsynchronous Locally Synchronous (GALS) NoCs with four-phase handshakecommunication protocol, using the actor-based modeling language Rebeca. Functionaland timing behaviors, routing algorithm and communication protocol are capturedin the model. Deadlock freedom, message arrival, and end-to-end packet latencyare checked. In order to analyze large NoCs we propose a scalable approachbased on compositional verification for estimating maximum end-to-end packet latency.The compositional approach is specific for the XY-routing algorithm. Resultsof verification are compared and matched to simulation results of HSPICE using32nm technology

Preface: Special issue on Foundations of Coordination Languages and Software Architectures (selected papers from FOCLASA'09)

International audienceThis issue contains extended versions of selected papers from the 8th International Workshop on the Foundations of Coordination Languages and Software Architectures (FOCLASA'09)

Performance Analysis of Distributed and Asynchronous Systems using Probabilistic Timed Actors

Many real-time distributed applications exhibit probabilistic and non-deterministic behaviors. In this paper, we introduce Probabilistic Timed Rebeca (PTRebeca) as an actor-based language for modeling probabilistic distributed real-time systems with asynchronous message passing. We propose the semantics of PTRebeca model in Timed Markov Decision Process (TMDP), the integral semantics of probabilistic timed automaton (PTA) with one digital clock. To analyze PTRebeca models, we develop a tool set to automatically generate a TMDP model from a PTRebeca model in the form of the input language of PRISM model checker. We use PRISM for performance analysis of PTRebeca models against expected reachability and probabilistic reachability properties. We show the applicability of our approach using a few case studies and experimental results

Specification and Verification of Timing Properties in Interoperable Medical Systems

To support the dynamic composition of various devices/apps into a medical system at point-of-care, a set of communication patterns to describe the communication needs of devices has been proposed. To address timing requirements, each pattern breaks common timing properties into finer ones that can be enforced locally by the components. Common timing requirements for the underlying communication substrate are derived from these local properties. The local properties of devices are assured by the vendors at the development time. Although organizations procure devices that are compatible in terms of their local properties and middleware, they may not operate as desired. The latency of the organization network interacts with the local properties of devices. To validate the interaction among the timing properties of components and the network, we formally specify such systems in Timed Rebeca. We use model checking to verify the derived timing requirements of the communication substrate in terms of the network and device models. We provide a set of templates as a guideline to specify medical systems in terms of the formal model of patterns. A composite medical system using several devices is subject to state-space explosion. We extend the reduction technique of Timed Rebeca based on the static properties of patterns. We prove that our reduction is sound and show the applicability of our approach in reducing the state space by modeling two clinical scenarios made of several instances of patterns

ConstScene: Dataset and Model for Advancing Robust Semantic Segmentation in Construction Environments

The increasing demand for autonomous machines in construction environments necessitates the development of robust object detection algorithms that can perform effectively across various weather and environmental conditions. This paper introduces a new semantic segmentation dataset specifically tailored for construction sites, taking into account the diverse challenges posed by adverse weather and environmental conditions. The dataset is designed to enhance the training and evaluation of object detection models, fostering their adaptability and reliability in real-world construction applications. Our dataset comprises annotated images captured under a wide range of different weather conditions, including but not limited to sunny days, rainy periods, foggy atmospheres, and low-light situations. Additionally, environmental factors such as the existence of dirt/mud on the camera lens are integrated into the dataset through actual captures and synthetic generation to simulate the complex conditions prevalent in construction sites. We also generate synthetic images of the annotations including precise semantic segmentation masks for various objects commonly found in construction environments, such as wheel loader machines, personnel, cars, and structural elements. To demonstrate the dataset's utility, we evaluate state-of-the-art object detection algorithms on our proposed benchmark. The results highlight the dataset's success in adversarial training models across diverse conditions, showcasing its efficacy compared to existing datasets that lack such environmental variability.Comment: 9 page

Formal Verification of Consistency for Systems with Redundant Controllers

A potential problem that may arise in the domain of distributed control systems is the existence of more than one primary controller in redundancy plans that may lead to inconsistency. An algorithm called NRP FD is proposed to solve this issue by prioritizing consistency over availability. In this paper, we demonstrate how by using modeling and formal verification, we discovered an issue in NRP FD where we may have two primary controllers at the same time. We then provide a solution to mitigate the identified issue, thereby enhancing the robustness and reliability of such systems.Comment: In Proceedings MARS 2024, arXiv:2403.1786

Comparing Three Coordination Models: Reo, ARC, and RRD

Abstract Three models of coordination-Reo, Actors-Roles-Coordinators (ARC), and Reflective Russian Dolls (RRD)-are compared and contrasted according to a set of coordination features. Mappings between their semantic models are defined. Use of the models is illustrated by a small case study