Abstract
Exceptional preferences mining (EPM) is a crossover between two subfields of data mining: local pattern mining and preference learning. EPM can be seen as a local pattern mining task that finds subsets of observations where some preference relations between labels significantly deviate from the norm. It is a variant of subgroup discovery, with rankings of labels as the target concept. We employ several quality measures that highlight subgroups featuring exceptional preferences, where the focus of what constitutes exceptional' varies with the quality measure: two measures look for exceptional overall ranking behavior, one measure indicates whether a particular label stands out from the rest, and a fourth measure highlights subgroups with unusual pairwise label ranking behavior. We explore a few datasets and compare with existing techniques. The results confirm that the new task EPM can deliver interesting knowledge.

Abstract
Electrum is an extension of Alloy that adds (1) mutable signatures and fields to the modeling layer; and (2) connectives from linear temporal logic (with past) and primed variables à la TLA+ to the constraint language. The analysis of models can then be translated into a SAT-based bounded model-checking problem, or to an LTL-based unbounded model-checking problem. Electrum has proved to be useful to model and verify dynamic systems with rich configurations. However, when specifying events, the tedious and sometimes error-prone handling of traces and frame conditions (similarly as in Alloy) remained necessary. In this paper, we introduce an extension of Electrum with a so-called “action” layer that addresses these questions. © Springer International Publishing AG, part of Springer Nature 2018.

Abstract
This paper reports on the development of a formal model for the Hybrid ERTMS/ETCS Level 3 concept in Electrum, a lightweight formal specification language that extends Alloy with mutable relations and temporal logic operators. We show how Electrum and its Analyzer can be used to perform scenario exploration to validate this model, namely to check that all the example operational scenarios described in the reference document are admissible, and to reason about expected safety properties, which can be easily specified and model checked for arbitrary track configurations. The Analyzer depicts scenarios (and counter-examples) in a graphical notation that is logic-agnostic, making them understandable for stakeholders without expertise in formal specification. © Springer International Publishing AG, part of Springer Nature 2018.

Abstract
This paper presents the Electrum Analyzer, a free-software tool to validate and perform model checking of Electrum specifications. Electrum is an extension of Alloy that enriches its relational logic with LTL operators, thus simplifying the specification of dynamic systems. The Analyzer supports both automatic bounded model checking, with an encoding into SAT, and unbounded model checking, with an encoding into SMV. Instance, or counter-example, traces are presented back to the user in a unified visualizer. Features to speed up model checking are offered, including a decomposed parallel solving strategy and the extraction of symbolic bounds. Source code: https://github.com/haslab/ElectrumVideo: https://youtu.be/FbjlpvjgMDA. © 2018 Copyright held by the owner/author(s).

Abstract
The Robot Operating System (ROS) is an open source framework for the development of robotic software, in which a typical system consists of multiple processes communicating under a publisher-subscriber architecture. A great deal of development time goes into orchestration and making sure that the communication interfaces comply with the expected contracts (e.g. receiving a message leads to the publication of another message). Orchestration mistakes are only detected during runtime, stressing the importance of component and integration testing in the verification process. Property-based Testing is fitting in this context, since it is based on the specification of contracts and treats tested components as black boxes, but there is no support for it in ROS. In this paper, we present a first approach towards automatic generation of test scripts for property-based testing of various configurations of a ROS system.

Abstract
In the area of algebraic specification there are two main approaches for defining observational abstraction: behavioural specifications use a notion of observational satisfaction for the axioms of a specification, whereas abstractor specifications define an abstraction from the standard semantics of a specification w.r.t. an observational equivalence relation between algebras. Earlier work by Bidoit, Hennicker, Wirsing has shown that in the case of first-order logic specifications both concepts coincide semantically under mild assumptions. Analogous results have been shown by Sannella and Hofmann for higher-order logic specifications and recently, by Hennicker and Madeira, for specifications of reactive systems using a dynamic logic with binders. In this paper, we bring these results into a common setting: we isolate a small set of characteristic principles to express the behaviour/abstractor equivalence and show that all three mentioned specification frameworks satisfy these principles and therefore their behaviour and abstractor specifications coincide semantically (under mild assumptions). As a new case we consider observational modal logic where observational satisfaction of Hennessy-Milner logic formulae is defined "up to" silent transitions and observational abstraction is defined by weak bisimulation. We show that in this case the behaviour/abstractor equivalence can only be obtained, if we restrict models to weakly deterministic labelled transition systems.