Software-product-line engineering has gained considerable momentum in the recent years, both in industry and in academia. A software product line is a family of software products that share a common set of features. Software product lines challenge traditional analysis techniques, such as type checking, model checking, and theorem proving, in their quest of ensuring correctness and reliability of software. Simply creating and analyzing all products of a product line is usually not feasible, due to the potentially exponential number of valid feature combinations. Recently, researchers began to develop analysis techniques that take the distinguishing properties of software product lines into account, for example, by checking feature-related code in isolation or by exploiting variability information during analysis. The emerging field of product-line analyses is both broad and diverse, so it is difficult for researchers and practitioners to understand their similarities and differences. We propose a classification of product-line analyses to enable systematic research and application. Based on our insights with classifying and comparing a corpus of 123 research articles, we develop a research agenda to guide future research on product-line analyses.

Feature-oriented programming (FOP) implements software product lines by composition of feature modules. It relies on the principles of stepwise development. Feature modules are intended to refer to exactly one product feature and can only extend existing implementations. To provide more flexibility for implementing software product lines, we propose delta-oriented programming (DOP) as a novel programming language approach. A product line is represented by a core module and a set of delta modules. The core module provides an implementation of a valid product that can be developed with well-established single application engineering techniques. Delta modules specify changes to be applied to the core module to implement further products by adding, modifying and removing code. Application conditions attached to delta modules allow handling combinations of features explicitly. A product implementation for a particular feature configuration is generated by applying incrementally all delta modules with valid application condition to the core module. In order to evaluate the potential of DOP, we compare it to FOP, both conceptually and empirically.

Delta-oriented programming is a compositional approach to flexibly implementing software product lines. A product line is represented by a code base and a product line declaration. The code base consists of a set of delta modules specifying modifications to object-oriented programs. A particular product in a delta-oriented product line is generated by applying the modifications contained in the suitable delta modules to the empty program. The product-line declaration provides the connection of the delta modules with the product features. This separation increases the reusability of delta modules. In this paper, we provide a foundation for compositional type checking of delta-oriented product lines of JAVA programs by presenting a minimal core calculus for delta-oriented programming. The calculus is equipped with a constraint-based type system that allows analyzing each delta module in isolation, such that the results of the analysis can be reused. By relying only on the analysis results for the delta modules and on the product line declaration, it is possible to establish whether all the products of the product line are well typed according to the fragment of the JAVA type system modeled by the calculus.

a b s t r a c tCoping with evolution in automated production systems implies a cross-disciplinary challenge along the system's life-cycle for variant-rich systems of high complexity. The authors from computer science and automation provide an interdisciplinary survey on challenges and state of the art in evolution of automated production systems. Selected challenges are illustrated on the case of a simple pick and place unit. In the first part of the paper, we discuss the development process of automated production systems as well as the different type of evolutions during the system's life-cycle on the case of a pick and place unit. In the second part, we survey the challenges associated with evolution in the different development phases and a couple of cross-cutting areas and review existing approaches addressing the challenges. We close with summarizing future research directions to address the challenges of evolution in automated production systems.

Delta-oriented programming (DOP) is a modular approach for implementing software product lines. Delta modules generalize feature modules by allowing removal of functionality. However, DOP requires to select one particular product as core product from which all products are generated. In this paper, we propose pure deltaoriented programming (Pure DOP) that is a conceptual simplification of traditional DOP. In Pure DOP, the requirement of one designated core product is dropped. Instead, program generation only relies on delta modules comprising program modifications such that Pure DOP is more flexible than traditional DOP. Furthermore, we show that Pure DOP is a true generalization of FOP and supports proactive, reactive and extractive product line engineering.