Ina Schaefer

Delta-oriented programming of software product lines

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.

A Classification and Survey of Analysis Strategies for Software Product Lines

Software-product-line engineering has gained considerable momentum in 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.

Software diversity: state of the art and perspectives

Diversity is prevalent in modern software systems to facilitate adapting the software to customer requirements or the execution environment. Diversity has an impact on all phases of the software development process. Appropriate means and organizational structures are required to deal with the additional complexity introduced by software variability. This introductory article to the special section “Software Diversity—Modeling, Analysis and Evolution” provides an overview of the current state of the art in diverse systems development and discusses challenges and potential solutions. The article covers requirements analysis, design, implementation, verification and validation, maintenance and evolution as well as organizational aspects. It also provides an overview of the articles which are part of this special section and addresses particular issues of diverse systems development.

Abstract delta modeling

Delta modeling is an approach to facilitate automated product derivation for software product lines. It is based on a set of deltas specifying modifications that are incrementally applied to a core product. The applicability of deltas depends on feature-dependent conditions. This paper presents abstract delta modeling, which explores delta modeling from an abstract, algebraic perspective. Compared to previous work, we take a more flexible approach with respect to conflicts between modifications and introduce the notion of conflict-resolving deltas. We present conditions on the structure of deltas to ensure unambiguous product generation.

Abstract delta modelling

Delta modelling is an approach to facilitate the automated product derivation for software product lines. It is based on a set of deltas specifying modifications that are incrementally applied to a core product. The applicability of deltas depends on application conditions over features. This paper presents abstract delta modelling , which explores delta modelling from an abstract, algebraic perspective. Compared to the previous work, we take a more flexible approach to conflicts between modifications by introducing the notion of conflict-resolving deltas. Furthermore, we extend our approach to allow the nesting of delta models for increased modularity. We also present conditions on the structure of deltas to ensure unambiguous product generation.

Incremental model-based testing of delta-oriented software product lines

Software product line (SPL) engineering provides a promising approach for developing variant-rich software systems. But, testing of every product variant in isolation to ensure its correctness is in general not feasible due to the large number of product variants. Hence, a systematic approach that applies SPL reuse principles also to testing of SPLs in a safe and efficient way is essential. To address this issue, we propose a novel, model-based SPL testing framework that is based on a delta-oriented SPL test model and regression-based test artifact derivations. Test artifacts are incrementally constructed for every product variant by explicitly considering commonality and variability between two consecutive products under test. The resulting SPL testing process is proven to guarantee stable test coverage for every product variant and allows the derivation of redundancy-reduced, yet reliable retesting obligations. We compare our approach with an alternative SPL testing strategy by means of a case study from the automotive domain.

Evolution of software in automated production systems

Automated Production Systems (aPS) impose specific requirements regarding evolution.We present a classification of how Automated Production Systems evolve.We discuss the state of art and research needs for the development phases of aPS.Model-driven engineering and Variability Management are key issues.Cross-discipline analysis of (non)-functional requirements must be improved. Coping with evolution in automated production systems implies a cross-disciplinary challenge along the systems 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 systems 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. Display Omitted

Pure delta-oriented programming

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 delta-oriented 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.

Compositional type-checking for delta-oriented programming

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. 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 that also the results of the analysis can be reused. By combining the analysis results for the delta modules with the product line declaration it is possible to establish that all the products of the product line are well-typed according to the Java type system.

Flexible product line engineering with a virtual platform

Cloning is widely used for creating new product variants. While it has low adoption costs, it often leads to maintenance problems. Long term reliance on cloning is discouraged in favor of systematic reuse offered by product line engineering (PLE) with a central platform integrating all reusable assets. Unfortunately, adopting an integrated platform requires a risky and costly migration. However, industrial experience shows that some benefits of an integrated platform can be achieved by properly managing a set of cloned variants. In this paper, we propose an incremental and minimally invasive PLE adoption strategy called virtual platform. Virtual platform covers a spectrum of strategies between ad-hoc clone and own and PLE with a fully-integrated platform divided into six governance levels. Transitioning to a governance level requires some effort and it provides some incremental benefits. We discuss tradeoffs among the levels and illustrate the strategy on an example implementation.