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Concurrent systems are hard to program, and ensuring quality by means of traditional testing techniques is often very hard as errors may not show up easily and reproducing them is hard. In previous work, we have advocated a model-driven approach to the analysis and design of concurrent, safety-critical systems. However, to take full advantage of these techniques, they must be supported by code generation schemes for concrete programming languages. Ideally, this translation should be traceable, automated and should support the verification of the generated code. In our work, we consider the problem of generating a concurrent Java component from a high-level model of inter-process interaction (i.e., communication + synchronization). We call our formalism shared resources. From the model, which can be represented in mathematical notation or written as a Java interface annotated using an extension of JML, a Java component can be obtained by a semiautomatic translation. We describe how to obtain shared memory (using a priority monitors library) and message passing (using the JCSP library) implementations. Focusing on inter-process interaction for formal development is justified by several reasons, e.g., mathematical models are language-independent and allow to analyze certain concurrency issues, such as deadlocks or liveness properties prior to code generation. Also, the Java components produced from the shared resource model will contain all the concurrency-related language constructs, which are often responsible for many of the errors in concurrent software. We follow a realistic approach where the translation is semiautomatic (schemata for code generation) and the programmer still retains the power of coding or modifying parts of the code for the resource. The code thus obtained is JML-annotated Java with proof obligations that help with code traceability and verification of safety and liveness properties. As the code thus obtained is not automatically correct, there is still the need to verify its conformance to the original specs. We illustrate the methodology by developing a concurrent control system and verifying the code obtained using the KeY program verification tool. We also show how KeY can be used to find errors resulting from a wrong use of the templates.

The current trends in next-generation exascale systems go towards integrating a wide range of specialized (co-)processors into traditional supercomputers. Due to the efficiency of heterogeneous systems in terms of Watts and FLOPS per surface unit, opening the access of heterogeneous platforms to a wider range of users is an important problem to be tackled. However, heterogeneous platforms limit the portability of the applications and increase development complexity due to the programming skills required. Program transformation can help make programming heterogeneous systems easier by defining a step-wise transformation process that translates a given initial code into a semantically equivalent final code, but adapted to a specific platform. Program transformation systems require the definition of efficient transformation strategies to tackle the combinatorial problem that emerges due to the large set of transformations applicable at each step of the process. In this paper we propose a machine learning-based approach to learn heuristics to define program transformation strategies. Our approach proposes a novel combination of reinforcement learning and classification methods to efficiently tackle the problems inherent to this type of systems. Preliminary results demonstrate the suitability of this approach., Comment: In Proceedings PROLE 2016, arXiv:1701.03069. This paper is based on arXiv:1603.03022, and has a thorough description of the proposed approach

The paper describes a framework for testing a class of safety-critical concurrent systems implemented using shared resource specifications. Shared resources contain declarative specifications of process interaction that can be used to derive, in a model-driven way, the most critical parts of a concurrent system. Here, we propose their use to build a state-based model that will help in testing a real implementation of the resource. The framework has been implemented using Erlang and QuickCheck and its source code is available. The paper also provides a novel parametric operational semantics for shared resources with scheduling policy annotations and a methodology to guide test-case generation from the shared resource specifications and a classification of common mistakes. We illustrate our framework by applying it to testing Java implementations of a prototypical automated shipping plant.

During its lifetime, a program suffers several changes that seek to improve or to augment some parts of its functionality. However, these modifications usually also introduce errors that affect the already-working code. There are several approaches and tools that help to spot and find the source of these errors. However, most of these errors could be avoided beforehand by using some of the knowledge that the programmers had when they were writing the code. This is the idea behind the design-by-contract approach, where users can define contracts that can be checked during runtime. In this paper, we apply the principles of this approach to Erlang, enabling, in this way, a runtime verification system in this language. We define two types of contracts. One of them can be used in any Erlang program, while the second type is intended to be used only in concurrent programs. We provide the details of the implementation of both types of contracts. Moreover, we provide an extensive explanation of each contract as well as examples of their usage. All the ideas presented in this paper have been implemented in a contract-based runtime verification system named EDBC. Its source code is available at GitHub as an open-source and free project., 19 pages, Accepted for presentation in WFLP 2018

We present an undergraduate course on concurrent programming where formal models are used in different stages of the learning process. The main practical difference with other approaches lies in the fact that the ability to develop correct concurrent software relies on a systematic transformation of formal models of inter-process interaction (so called shared resources ), rather than on the specific constructs of some programming language. Using a resource-centric rather than a language-centric approach has some benefits for both teachers and students. Besides the obvious advantage of being independent of the programming language, the models help in the early validation of concurrent software design, provide students and teachers with a lingua franca that greatly simplifies communication at the classroom and during supervision, and help in the automatic generation of tests for the practical assignments. This method has been in use, with slight variations, for some 15 years, surviving changes in the programming language and course length. In this article, we describe the components and structure of the current incarnation of the course—which uses Java as target language—and some tools used to support our method. We provide a detailed description of the different outcomes that the model-driven approach delivers (validation of the initial design, automatic generation of tests, and mechanical generation of code) from a teaching perspective. A critical discussion on the perceived advantages and risks of our approach follows, including some proposals on how these risks can be minimized. We include a statistical analysis to show that our method has a positive impact in the student ability to understand concurrency and to generate correct code.

We present a declarative framework for the compilation of constraint logic programs into variable-free relational theories which are then executed by rewriting. This translation provides an algebraic formulation of the abstract syntax of logic programs. Logic variables, unification, and renaming apart are completely elided in favor of manipulation of variable-free relation expressions. In this setting, term rewriting not only provides an operational semantics for logic programs, but also a simple framework for reasoning about program execution. We prove the translation sound, and the rewriting system complete with respect to traditional SLD semantics.

This article describes a systematic approach to testing behavioural aspects of Web Services that communicate using the JSON data format. As a key component, the Quviq QuickCheck property-based testing tool is used to automatically generate a large number of test cases from an abstract description of the service behaviour in the form of a finite state machine. The same behavioural description is also used to decide whether the execution of a test case is successful or not. To generate random JSON data for populating tests we have developed a new library, jsongen, which given a characterisation of the JSON data as a JSON schema, (i) automatically derives a QuickCheck generator which can generate an infinite number of JSON values that validate against the schema, and (ii) provides a generic QuickCheck state machine which is capable of following the (hyper)links documented in the JSON schema, to automatically explore the web service. The default behaviour of the state machine can be easily customized to include web service specific checks. The article illustrates the approach by developing a finite state machine model for the testing of a JSON-based web service.

Testing is the more widely used approach to (partial) system validation in industry. The introduction of concurrency makes exhaustive testing extremely costly or just impossible, requiring shifting to formal verification techniques. We propose a methodology to design and verify a concurrent system that splits the verification problem in two independent tasks: internal verification of shared resources, where some concurrency aspects like mutual exclusion and conditional synchronisation are isolated, and external verification of processes, where synchronisation mechanisms are not relevant. Our method is language independent, non-intrusive for the development process, and improves the portability of the resulting system. We demonstrate it by actually checking several properties of an example application using the TLC model checker.