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.

Abstract
Parallelizing rendering algorithms to exploit multiprocessor and multicore machines isn't straightforward. Certain methods require frequent synchronization among threads to obtain benefits similar to the sequential algorithm. One such algorithm is the irradiance cache (IC), an acceleration data structure that caches indirect diffuse irradiance values. In multicore systems, the threads must share the IC to achieve high efficiency. A proposed wait-free mechanism for accessing the shared IC doesn't use the common blocking or busy-waiting methods, thus avoiding most serialization and reducing contention. A comparison with two classic approachesa lock-based mechanism and a local-write techniqueon two systems with up to 24 cores shows that the wait-free approach significantly reduces synchronization overhead, thus improving performance. The Web extra PDF augments the article. The Web extra video is an animation that demonstrates the wait-free IC system running at close to interactive rates on an 8-core machine. © 2006 IEEE.

Abstract

Abstract
Within the development of motor vehicles, crash safety (e.g. occupant protection, pedestrian protection, low speed damageability), is one of the most important attributes. In order to be able to fulfill the increased requirements in the framework of shorter cycle times and rising pressure to reduce costs, car manufacturers keep intensifying the use of virtual development tools such as those in the domain of Computer Aided Engineering (CAE). For crash simulations, the explicit finite element method (FEM) is applied. The accuracy of the simulation process is highly dependent on the accuracy of the simulation model, including the midplane mesh. One of the roughest approximations typically made is the actual part thickness which, in reality, can vary locally. However, almost always a constant thickness value is defined throughout the entire part due to complexity reasons. On the other hand, for precise fracture analysis within FEM, the correct thickness consideration is one key enabler. hus, availability of per element thickness information, which does not exist explicitly in the FEM model, can significantly contribute to an improved crash simulation quality, especially regarding fracture prediction. Even though the thickness is not explicitly available from the FEM model, it can be inferred from the original CAD geometric model through geometric calculations. This paper proposes and compares two thickness estimation algorithms based on ray tracing and nearest neighbour 3D range searches. A systematic quantitative analysis of the accuracy of both algorithms is presented, as well as a thorough identification of particular geometric arrangements under which their accuracy an be compared. These results enable the identification of each technique's weaknesses and hint towards a new, integrated, approach to the problem that linearly combines the estimates produced by each algorithm.

Abstract