An Algebra of Synchronous Scheduling Interfaces

In this paper we propose an algebra of synchronous scheduling interfaces which combines the expressiveness of Boolean algebra for logical and functional behaviour with the min-max-plus arithmetic for quantifying the non-functional aspects of synchronous interfaces. The interface theory arises from a realisability interpretation of intuitionistic modal logic (also known as Curry-Howard-Isomorphism or propositions-as-types principle). The resulting algebra of interface types aims to provide a general setting for specifying type-directed and compositional analyses of worst-case scheduling bounds. It covers synchronous control flow under concurrent, multi-processing or multi-threading execution and permits precise statements about exactness and coverage of the analyses supporting a variety of abstractions. The paper illustrates the expressiveness of the algebra by way of some examples taken from network flow problems, shortest-path, task scheduling and worst-case reaction times in synchronous programming.Comment: In Proceedings FIT 2010, arXiv:1101.426

Causality in the Semantics of Esterel: Revisited

We re-examine the challenges concerning causality in the semantics of Esterel and show that they pertain to the known issues in the semantics of Structured Operational Semantics with negative premises. We show that the solutions offered for the semantics of SOS also provide answers to the semantic challenges of Esterel and that they satisfy the intuitive requirements set by the language designers

Expressing the Behavior of Three Very Different Concurrent Systems by Using Natural Extensions of Separation Logic

Separation Logic is a non-classical logic used to verify pointer-intensive code. In this paper, however, we show that Separation Logic, along with its natural extensions, can also be used as a specification language for concurrent-system design. To do so, we express the behavior of three very different concurrent systems: a Subway, a Stopwatch, and a 2x2 Switch. The Subway is originally implemented in LUSTRE, the Stopwatch in Esterel, and the 2x2 Switch in Bluespec

Hop and HipHop : Multitier Web Orchestration

Rich applications merge classical computing, client-server concurrency, web-based interfaces, and the complex time- and event-based reactive programming found in embedded systems. To handle them, we extend the Hop web programming platform by HipHop, a domain-specific language dedicated to event-based process orchestration. Borrowing the synchronous reactive model of Esterel, HipHop is based on synchronous concurrency and preemption primitives that are known to be key components for the modular design of complex reactive behaviors. HipHop departs from Esterel by its ability to handle the dynamicity of Web applications, thanks to the reflexivity of Hop. Using a music player example, we show how to modularly build a non-trivial Hop application using HipHop orchestration code.Comment: International Conference on Distributed Computing and Internet Technology (2014

The Kiel Esterel Processor - A Semi-Custom, Configurable Reactive Processor

The synchronous language Esterel is an established language for developing reactive systems. It gives an abstract, well-defined and executable description of the application, and can be synthesized into hardware and software. Typically, an Esterel program is first translated into other, lower-level languages (such as VHDL or C), and then compiled further. However, there is also the alternative of executing Esterel-like instructions directly. For example, in the REFLIX and RePIC projects, Roop et al. have augmented traditional processors with custom hardware to execute Esterel instructions. This patch strategy is a convenient approach, but has some shortages. We present the Kiel Esterel Processor (KEP), a semi-custom, configurable reactive processor for the direct execution of Esterel programs. It consists of a reactive core and scalable peripheral elements. KEP supports standard Esterel statements directly, except (so far) for the concurrency operator. Valued signals and counter functions in Esterel statements are supported by KEP. Due to its control path and its cooperation with elements, KEP obeys exact Esterel (preemption and priority) rules, including for example abort/weak abort (nests)

Reactive concurrent programming revisited

In this note we revisit the so-called reactive programming style, which evolves from the synchronous programming model of the Esterel language by weakening the assumption that the absence of an event can be detected instantaneously. We review some research directions that have been explored since the emergence of the reactive model ten years ago. We shall also outline some questions that remain to be investigated

Approximate Reachability for Dead Code Elimination in Esterel*

Esterel is an imperative synchronous programming language for the design of reactive systems. Esterel* extends Esterel with a non-instantaneous jump instruction (compatible with concurrency, preemption, etc.) so as to enable powerful source-to-source program transformations, amenable to formal verification. In this work, we propose an approximate reachability algorithm for Esterel* and use its output to remove dead code. We prove the correctness of our techniques