Treo: Textual Syntax for Reo Connectors

Reo is an interaction-centric model of concurrency for compositional specification of communication and coordination protocols. Formal verification tools exist to ensure correctness and compliance of protocols specified in Reo, which can readily be (re)used in different applications, or composed into more complex protocols. Recent benchmarks show that compiling such high-level Reo specifications produces executable code that can compete with or even beat the performance of hand-crafted programs written in languages such as C or Java using conventional concurrency constructs. The original declarative graphical syntax of Reo does not support intuitive constructs for parameter passing, iteration, recursion, or conditional specification. This shortcoming hinders Reo's uptake in large-scale practical applications. Although a number of Reo-inspired syntax alternatives have appeared in the past, none of them follows the primary design principles of Reo: a) declarative specification; b) all channel types and their sorts are user-defined; and c) channels compose via shared nodes. In this paper, we offer a textual syntax for Reo that respects these principles and supports flexible parameter passing, iteration, recursion, and conditional specification. In on-going work, we use this textual syntax to compile Reo into target languages such as Java, Promela, and Maude.Comment: In Proceedings MeTRiD 2018, arXiv:1806.0933

Reconfigurable component connectors

This thesis provides formal methods for reconfigurable component connectors.UBL - phd migration 201

Safety and Performance in Generated Coordination Code

Reo is able to act as a domain specific language by compiling a high-level protocol specification to coordination glue code in a target general purpose language. In the case of Java, these generated programs take advantage of optimization opportunities, but struggle to preserve Reo’s semantics. In this work, we extend the Reo compiler to support the Rust language. We show that the resulting programs implement several existing and novel performance optimizations, whilst relying on Rust’s expressive type system to preserve meaningful safety and liveness properties at compile time. Our data-oriented design facilitates flexibility, such as protocol reconfiguration at runtime, but still achieves performance in the order of handcrafted programs for non-trivial protocols

Formal Techniques for Component-based Design of Embedded Systems

Embedded systems have become ubiquitous - from avionics and automotive over consumer electronics to medical devices. Failures may entailmaterial damage or compromise safety of human beings. At the same time, shorter product cycles, together with fast growing complexity of the systems to be designed, create a tremendous need for rigorous design techniques. The goal of component-based construction is to build complex systems from simpler components that are well understood and can be (re)used so as to accelerate the design process. This document presents a summary of the formal techniques for component-based design of embedded systems I have (co-)developed

Centralized coordination vs. partially-distributed coordination with Reo and constraint automata

High-level concurrency notations and abstractions have several well-known software engineering advantages when it comes to programming concurrency protocols among threads. To also explore their complementary performance advantages, in ongoing work, we are developing compilation technology for a high-level coordination language, Reo, based on this language's formal automaton semantics. By now, as shown in our previous work, our tools are capable of generating code that can compete with carefully handcrafted code, at least for some protocols. An important prerequisite to further advance this promising technology, now, is to gain a better understanding of how the significantly different compilation approaches that we developed so far, which vary in the amount of parallelism in their generated code, compare against each other. For instance, to better and more reliably tune our compilers, we must learn under which circumstances parallel protocol code, with high throughput but also high latency, outperforms sequential protocol code, with low latency but also low throughput. In this paper, we report on an extensive performance comparison between these approaches for a substantial number of protocols, expressed in Reo. Because we have always formulated our compilation technology in terms of a general kind of communicating automaton (i.e., constraint automata), our findings apply not only to Reo but, in principle, to any language whose semantics can be defined in terms of such automata. (C) 2017 Elsevier B.V. All rights reserved

A framework for robust control of uncertainty in self-adaptive software connectors

Context and motivations. The desired behavior of a system in ubiquitous environments considers not only its correct functionality, but also the satisfaction of its non-functional properties, i.e., its quality of service. Given the heterogeneity and dynamism characterizing the ubiquitous environments and the need for continuous satisfaction of non-functional properties, self-adaptive solutions appear to be an appropriate approach to achieve interoperability. In this work, self-adaptation is adopted to enable software connectors to adapt the interaction protocols run by the connected components to let them communicate in a timely manner and with the required level of quality. However, this self-adaptation should be dependable, reliable and resilient to be adopted in dynamic, unpredictable environments with different sources of uncertainty. The majority of current approaches for the construction of self-adaptive software ignore the uncertainty underlying non-functional requirement verification and adaptation reasoning. Consequently, these approaches jeopardize system reliability and hinder the adoption of self-adaptive software in areas where dependability is of utmost importance. Objective. The main objective of this research is to properly handle the uncertainties in the non-functional requirement verification and the adaptation reasoning part of the self-adaptive feedback control loop of software connectors. This will enable a robust and runtime efficient adaptation in software connectors and make them reliable for usage in uncertain environments. Method. In the context of this thesis, a framework has been developed with the following functionalities: 1) Robust control of uncertainty in runtime requirement verification. The main activity in runtime verification is fine-tuning of the models that are adopted for runtime reasoning. The proposed stochastic approach is able to update the unknown parameters of the models at runtime even in the presence of incomplete and noisy observations. 2) Robust control of uncertainty in adaptation reasoning. A general methodology based on type-2 fuzzy logic has been introduced for the control of adaptation decision-making that adjusts the configuration of component connectors to the appropriate mode. The methodology enables a systematic development of fuzzy logic controllers that can derive the right mode for connectors even in the presence of measurement inaccuracy and adaptation policy conflicts. Results. The proposed model evolution mechanism is empirically evaluated, showing a significant precision of parameter estimation with an acceptable overhead at runtime. In addition, the fuzzy based controller, generated by the methodology, has been shown to be robust against uncertainties in the input data, efficient in terms of runtime overhead even in large-scale knowledge bases and stable in terms of control theory properties. We also demonstrate the applicability of the developed framework in a real-world domain. Thesis statement. We enable reliable and dependable self-adaptations of component connectors in unreliable environments with imperfect monitoring facilities and conflicting user opinions about adaptation policies by developing a framework which comprises: (a) mechanisms for robust model evolution, (b) a method for adaptation reasoning, and (c) tool support that allows an end-to-end application of the developed techniques in real-world domains