Abstract
Coordination in R eo emerges from the composition of the behavioural constraints of the primitives, such as channels, in a component connector. Understanding and implementing R eo, however, has been challenging due to interaction of the channel metaphor, which is an inherently local notion, and the non-local nature of constraint propagation imposed by composition. In this paper, the channel metaphor takes a back seat, and we focus on the behavioural constraints imposed by the composition of primitives, and phrase the semantics of R eo as a constraint satisfaction problem. Not only does this provide a clear intensional description of the behaviour of R eo connectors in terms of synchronisation and data flow constraints, it also paves the way for new implementation techniques based on constraint propagation and satisfaction. In fact, decomposing R eo into constraints provides a new computational model for connectors, which we extend to model interaction with an unknown external world beyond what is currently possible in R eo.

Abstract
Since wireless sensor network applications are ever growing in scale and complexity, managers require strong formal guarantees that any changes done to the system can be enacted safely. This paper presents the formalisation and analysis of the semantics of policies, tiny software artefacts used to orchestrate wireless sensor network applications. The semantics of policies is formalised in terms of traces augmented with information concerning the constraints under which traces are executed. These traces are composed according to the network topology and subsequently analysed using the mCRL2 model-checking tool. The analysis allows for the detection of semantical inconsistencies that may lead to dangerous or unwanted behaviour of the application based on the policy configuration. An analysis of policies in a real-world system is provided, showing how to verify security and resource usage properties. © 2012 IEEE.

Abstract
Modern software systems must support a high degree of variability to accommodate a wide range of requirements and operating conditions. This paper introduces the Abstract Behavioural Specification (ABS) language and tool suite, a comprehensive platform for developing and analysing highly adaptable distributed concurrent software systems. The ABS language has a hybrid functional and object- oriented core, and comes with extensions that support the development of systems that are adaptable to diversified requirements, yet capable to maintain a high level of trustworthiness. Using ABS, system variability is consistently traceable from the level of requirements engineering down to object behaviour. This facilitates temporal evolution, as changes to the required set of features of a system are automatically reflected by functional adaptation of the system's behaviour. The analysis capabilities of ABS stretch from debugging, observing and simulating to resource analysis of ABS models and help ensure that a system will remain dependable throughout its evolutionary lifetime. We report on the experience of using the ABS language and the ABS tool suite in an industrial case study. © 2012 Springer-Verlag.

Abstract
Connector colouring provided an intuitive semantics of Reo connectors which lead to effective implementation techniques, first based on computing colouring tables directly, and later on encodings of colouring into constraints. One weakness of the framework is that it operates globally, giving a colouring to all primitives of the connector in lock-step, including those not involved in the interaction. This global approach limits both scalability and the available concurrency. This paper addresses these problems by introducing partiality into the connector colouring model. Partial colourings allow parts of a connector to operate independently and in isolation, increasing scalability and concurrency. © 2012 IFIP International Federation for Information Processing.

Abstract
The HATS project aims at developing a model-centric methodology for the design, implementation and verification of highly configurable systems, such as software product lines, centred around the Abstract Behavioural Specification (ABS) modelling Language. This article describes the variability modelling features of the ABS Modelling framework. It consists of four languages, namely, µTVL for describing feature models at a high level of abstraction, the Delta Modelling Language DML for describing variability of the 'code' base in terms of delta modules, the Product Line Configuration Language CL for linking feature models and delta modules together and the Product Selection Language PSL for describing a specific product to extract from a product line. Both formal semantics and examples of each language are presented. © 2011 Springer-Verlag Berlin Heidelberg.

Abstract
Formal modelling and verification are critical for managing the inherent complexity of systems with a high degree of variability, such as those designed following the software product line (SPL) paradigm. SPL models tend to be large-the number of products in an SPL can be exponential in the number of features. Modelling these systems poses two main challenges. Firstly, a modular modelling formalism that scales well is required. Secondly, the ability to analyse and verify complex models efficiently is key in order to ensure that all products behave correctly. The choice of a system modelling formalism that is both expressive and well-established is therefore crucial. In this paper we show how SPLs can be modelled in an incremental, modular fashion using a formal method based on Petri nets. We continue our work on Feature Petri Nets, a lightweight extension to Petri nets, by presenting a framework for modularly constructing Feature Petri Nets to model SPLs. © 2011 Springer-Verlag.