Equivalence associée à la relation de conformité "conf" et simplification du testeur canonique en LOTOS

peer reviewe

Conformance Testing with Labelled Transition Systems: Implementation Relations and Test Generation

This paper studies testing based on labelled transition systems, presenting two test generation algorithms with their corresponding implementation relations. The first algorithm assumes that implementations communicate with their environment via symmetric, synchronous interactions. It is based on the theory of testing equivalence and preorder, as is most of the testing theory for labelled transition systems, and it is found in the literature in some slightly different variations. The second algorithm is based on the assumption that implementations communicate with their environment via inputs and outputs. Such implementations are formalized by restricting the class of labelled transition systems to those systems that can always accept input actions. For these implementations a testing theory is developed, analogous to the theory of testing equivalence and preorder. It consists of implementation relations formalizing the notion of conformance of these implementations with respect to labelled transition system specifications, test cases and test suites, test execution, the notion of passing a test suite, and the test generation algorithm, which is proved to produce sound test suites for one of the implementation relations

Analysing Coloured Petri Nets by the Occurrence Graph Method

This paper provides an overview og the work done for the author's PhD thesis. The research area of Coloured Petri Nets is introduced, and the available analysis methods are presented. The occurrence graph method, which is the main subject of this thesis, is described in more detail. Summaries of the six papers which, together with this overview, comprise the thesis are given, and the contributions are discussed.A large portion of this overview is dedicated to a description of related work. The aim is twofold: First, to survey pertinent results within the research areas of -- in increasing generality -- Coloured Petri Nets, High-level Petri Nets, and formalisms for modelling and analysis of parallel and distributed systems. Second, to put the results obtained in this thesis in a wider perspective by comparing them with important related work

Linear vs. branching time: A semantical perspective

The discussion of the relative merits of linear versus branching-time goes back to early 1980s. The dominating belief has been that the linear-time framework is not expressive enough semantically, marking linear-time logics as weak. Here we examine this issue from the perspective of process equivalence, one of the most fundamental notions in concurrency theory. We postulate three principles that we view as fundamental to any discussion of process equivalence. First, we take contextual equivalence as the primary notion of equivalence. Second, we require the description of a process to fully specify all relevant behavioral aspects of the process. Finally, we require observable process behavior to be reflected in input/output behavior. Under these postulates the distinctions between the linear and branching semantics tend to evaporate. Applying them to the framework of transducers, we show that our postulates result in a unique notion of process equivalence, which is trace based, rather than tree based

Programming Languages and Systems

This open access book constitutes the proceedings of the 30th European Symposium on Programming, ESOP 2021, which was held during March 27 until April 1, 2021, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg and changed to an online format due to the COVID-19 pandemic. The 24 papers included in this volume were carefully reviewed and selected from 79 submissions. They deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

Formal Specification and Verification for Automated Production Systems

Complex industrial control software often drives safety- and mission-critical systems, like automated production plants or control units embedded into devices in automotive systems. Such controllers have in common that they are reactive systems, i.e., that they periodically read sensor stimuli and cyclically execute the same program to produce actuator signals. The correctness of software for automated production is rarely verified using formal techniques. Although, due to the Industrial Revolution 4.0 (IR4.0), the impact and importance of software have become an important role in industrial automation. What is used instead in industrial practice today is testing and simulation, where individual test cases are used to validate an automated production system. Three reasons why formal methods are not popular are: (a) It is difficult to adequately formulate the desired temporal properties. (b) There is a lack of specification languages for reactive systems that are both sufficiently expressive and comprehensible for practitioners. (c) Due to the lack of an environment model the obtained results are imprecise. Nonetheless, formal methods for automated production systems are well studied academically---mainly on the verification of safety properties via model checking. In this doctoral thesis we present the concept of (1) generalized test tables (GTTs), a new specification language for functional properties, and their extension (2) relational test tables (RTTs) for relational properties. The concept includes the syntactical notion, designed for the intuition of engineers, and the semantics, which are based on game theory. We use RTTs for a novel confidential property on reactive systems, the provably forgetting of information. Moreover, for regression verification, an important relational property, we are able to achieve performance improvements by (3) creating a decomposing rule which splits large proofs into small sub-task. We implemented the verification procedures and evaluated them against realistic case studies, e.g., the Pick-and-Place-Unit from the Technical University of Munich. The presented contribution follows the idea of lowering the obstacle of verifying the dependability of reactive systems in general, and automated production systems in particular for the engineer either by introducing a new specification language (GTTs), by exploiting existing programs for the specification (RTTs, regression verification), or by improving the verification performance

A Corpus-Based Investigation of Idiomatic Multiword Units

Idioms - a type of multiword unit (MWU) - are defined as being non-compositional and in general cannot be understood by adding together the meanings of the individual words that comprise the MWU. Because of this, they present a particular challenge to students who speak English as a second- or foreign-language (ESL/EFL). As a teacher of second-language (L2) learners, it is just that challenge which has motivated this study. Specifically, there were two main aims of the thesis. In order to know how to teach idioms to ESL/EFL learners, we - as language teachers - need to know how to define and explain them. Therefore, the first aim of the study was to either find an English (L1) definition of an idiom which could clearly distinguish one type from another, and an idiom from a non-idiom, or to develop a new definition. Having not found such a definition, a new definition was put forward, dividing MWUs presently known as idioms into three new groups - core idioms, figuratives, and ONCEs (one noncompositional element). The L1 perspective was adopted for the definition as an L2 perspective would involve considerably more variables. The second aim was to develop a comprehensive list of one of the three new groups - core idioms - and then try to establish frequency, using a corpus search. A number of steps were taken to compile this list, involving an examination of several sources of written and spoken English. The result was that when the criteria established to define a core idiom - being both non-compositional and non-figurative - were strictly applied to the large collection of MWUs presently known as 'idioms', the figure was reduced to only 104 MWUs deemed to be either core idioms or 'borderline figuratives' and 'borderline ONCEs'. Next the British National Corpus (BNC), a corpus of 100 million words, was searched for occurrences of these 104 core idioms and borderlines to establish their frequency. The result of the corpus search showed that none of the core idioms occurs frequently enough to get into the most frequent 5,000 words of English. However, as the motivation to do the study was the desire to find a better way to teach idiomatic MWUs, a brief discussion followed with suggestions for the teaching and learning of these idiomatic MWUs. Finally, some methodological implications and suggestions for future research were put forward, looking at further research which would advance the field of second-language acquisition (SLA) related to the learning of idiomatic MWUs