Paper Accepted at Coordination 2016

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An Interference-Free Programming Model for Network Objects by Mischael Schill, myself, and Bertrand Meyer was accepted for publication at the 18th IFIP International Conference on Coordination Models and Languages (COORDINATION 2016).

Network objects are a simple and natural abstraction for distributed object-oriented programming. Languages that support network objects, however, often leave synchronization to the user, along with its associated pitfalls, such as data races and the possibility of failure. In this paper, we present D-SCOOP, a distributed programming model that allows for interference-free and transaction-like reasoning on (potentially multiple) network objects, with synchronization handled automatically, and network failures managed by a compensation mechanism. We achieve this by leveraging the runtime semantics of a multi-threaded object-oriented concurrency model, directly generalizing it with a message-based protocol for efficiently coordinating remote objects. We present our pathway to fusing these contrasting but complementary ideas, and evaluate the performance overhead of the automatic synchronization in D-SCOOP, finding that it comes close to—or outperforms—explicit locking-based synchronization in Java RMI.

Paper postprint (.pdf)

Paper postprint (.pdf)

Paper Accepted at FASE 2016

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FASE at ETAPS 2016

FASE at ETAPS 2016

A Graph-Based Semantics Workbench for Concurrent Asynchronous Programs by Claudio Corrodi, Alexander Heußner, and myself was accepted for publication at the International Conference on Fundamental Approaches to Software Engineering (FASE 2016).

A number of novel programming languages and libraries have been proposed that offer simpler-to-use models of concurrency than threads. It is challenging, however, to devise execution models that successfully realise their abstractions without forfeiting performance or introducing unintended behaviours. This is exemplified by SCOOP—a concurrent object-oriented message-passing language—which has seen multiple semantics proposed and implemented over its evolution. We propose a “semantics workbench” with fully and semi-automatic tools for SCOOP, that can be used to analyse and compare programs with respect to different execution models. We demonstrate its use in checking the consistency of semantics by applying it to a set of representative programs, and highlighting a deadlock-related discrepancy between the principal execution models of the language. Our workbench is based on a modular and parameterisable graph transformation semantics implemented in the GROOVE tool. We discuss how graph transformations are leveraged to atomically model intricate language abstractions, and how the visual yet algebraic nature of the model can be used to ascertain soundness.

Paper postprint (.pdf)

Paper postprint (.pdf)

Presentation slides (.pdf)

Presentation slides (.pdf)

Paper Accepted at GaM 2015

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GaM 2015

GaM 2015

Towards Practical Graph-Based Verification for an Object-Oriented Concurrency Model by Alexander Heußner, myself, Claudio Corrodi, and Benjamin Morandi was accepted for publication at the Graphs as Models Workshop (GaM 2015).

To harness the power of multi-core and distributed platforms, and to make the development of concurrent software more accessible to software engineers, different object-oriented concurrency models such as SCOOP have been proposed. Despite the practical importance of analysing SCOOP programs, there are currently no general verification approaches that operate directly on program code without additional annotations. One reason for this is the multitude of partially conflicting semantic formalisations for SCOOP (either in theory or by-implementation). Here, we propose a simple graph transformation system (GTS) based run-time semantics for SCOOP that grasps the most common features of all known semantics of the language. This run-time model is implemented in the state-of-the-art GTS tool GROOVE, which allows us to simulate, analyse, and verify a subset of SCOOP programs with respect to deadlocks and other behavioural properties. Besides proposing the first approach to verify SCOOP programs by automatic translation to GTS, we also highlight our experiences of applying GTS (and especially GROOVE) for specifying semantics in the form of a run-time model, which should be transferable to GTS models for other concurrent languages and libraries.

Paper postprint (.pdf)

Paper postprint (.pdf)