A Graph-Based Semantics Workbench for Concurrent Asynchronous Programs

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.Comment: Accepted for publication in the proceedings of FASE 2016 (to appear

Solving the Mystery of Intrusive Flashbacks in Posttraumatic Stress Disorder (Comment on Brewin 2014)

"This article may not exactly replicate the final version published in the APA journal. It is not the copy of record."In the light of current controversy about the nature of intrusions in posttraumatic stress disorder (PTSD), the review by Brewin (2014) is timely and important. It will undoubtedly stimulate further research and guide researchers' quests for understanding the nature of flashbacks in PTSD. In this commentary, I briefly summarize and discuss key points made by Brewin and elaborate on some of the reasons behind the controversy. For example, the terms involuntary autobiographical memories, intrusive memories, and flashbacks are often used interchangeably. I propose a taxonomy revealing the key differences across these forms of memory. If flashbacks are characteristic of patients with PTSD only, it is essential that more research targeting this population is conducted with a variety of methods. Finally, some new avenues for research to study intrusive memories and flashbacks in PTSD, using a diary method and modified trauma film paradigm, are described.Peer reviewedSubmitted Versio

Stone-Type Dualities for Separation Logics

Stone-type duality theorems, which relate algebraic and relational/topological models, are important tools in logic because -- in addition to elegant abstraction -- they strengthen soundness and completeness to a categorical equivalence, yielding a framework through which both algebraic and topological methods can be brought to bear on a logic. We give a systematic treatment of Stone-type duality for the structures that interpret bunched logics, starting with the weakest systems, recovering the familiar BI and Boolean BI (BBI), and extending to both classical and intuitionistic Separation Logic. We demonstrate the uniformity and modularity of this analysis by additionally capturing the bunched logics obtained by extending BI and BBI with modalities and multiplicative connectives corresponding to disjunction, negation and falsum. This includes the logic of separating modalities (LSM), De Morgan BI (DMBI), Classical BI (CBI), and the sub-classical family of logics extending Bi-intuitionistic (B)BI (Bi(B)BI). We additionally obtain as corollaries soundness and completeness theorems for the specific Kripke-style models of these logics as presented in the literature: for DMBI, the sub-classical logics extending BiBI and a new bunched logic, Concurrent Kleene BI (connecting our work to Concurrent Separation Logic), this is the first time soundness and completeness theorems have been proved. We thus obtain a comprehensive semantic account of the multiplicative variants of all standard propositional connectives in the bunched logic setting. This approach synthesises a variety of techniques from modal, substructural and categorical logic and contextualizes the "resource semantics" interpretation underpinning Separation Logic amongst them

Towards Practical Graph-Based Verification for an Object-Oriented Concurrency Model

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.Comment: In Proceedings GaM 2015, arXiv:1504.0244

Identifying the Dimensions of Integrity: A Confirmatory and Discriminant Validity Analysis

While Integrity tests have demonstrated significant predictive and concurrent validity, the meaning and structure of integrity test scores are not well understood. The purpose of the present investigation was to empirically verify the results of a previous study that used an inductive method to define integrity and identify its constituent dimensions (Green, 1999). Specifically, the present investigation used item analysis, confirmatory factor analysis, discriminant validity analysis, and an analysis of social desirability to test the validity of the five integrity dimensions identified by Green (1999): Concern for Others, Conscientiousness, Emotional Control, Fairness, and Honesty. Results confirmed that Integrity acts as a second-order factor with multiple first-order dimensions. Four of the hypothesized first-order dimensions were confirmed in the study: Concern for Others, Conscientiousness, Emotional Control, and Honesty. The inadequacy of the Fairness measures made it impossible to test the relationship of this fifth dimension to the Integrity construct. A discriminant validity analysis failed to support the Integrity dimensions by indicating that Anticipated Tenure was significantly related to the Integrity construct. Also investigated was the influence of social desirability. Results indicated that social desirability influenced, but did not destroy the factor structure of the Integrity construct. Future research into the semantic realm of integrity is suggested

Study of Tools Interoperability

Interoperability of tools usually refers to a combination of methods and techniques that address the problem of making a collection of tools to work together. In this study we survey different notions that are used in this context: interoperability, interaction and integration. We point out relation between these notions, and how it maps to the interoperability problem. We narrow the problem area to the tools development in academia. Tools developed in such environment have a small basis for development, documentation and maintenance. We scrutinise some of the problems and potential solutions related with tools interoperability in such environment. Moreover, we look at two tools developed in the Formal Methods and Tools group1, and analyse the use of different integration techniques

Issues about the Adoption of Formal Methods for Dependable Composition of Web Services

Web Services provide interoperable mechanisms for describing, locating and invoking services over the Internet; composition further enables to build complex services out of simpler ones for complex B2B applications. While current studies on these topics are mostly focused - from the technical viewpoint - on standards and protocols, this paper investigates the adoption of formal methods, especially for composition. We logically classify and analyze three different (but interconnected) kinds of important issues towards this goal, namely foundations, verification and extensions. The aim of this work is to individuate the proper questions on the adoption of formal methods for dependable composition of Web Services, not necessarily to find the optimal answers. Nevertheless, we still try to propose some tentative answers based on our proposal for a composition calculus, which we hope can animate a proper discussion