Variability Challenges

Systems and Software Variability Challenges
The official website of the Systems and Software Product Line Conference challenge track

Current SPLC

SPLC 2019 Accepted Solutions

Richard Müller and Ulrich Eisenecker. “A Graph-based Feature Location Approach using Set Theory”.
Jeho Oh, Paul Gazzillo and Don Batory. “t-wise Coverage by Uniform Sampling”.
Gabriela Karoline Michelon, Lukas Linsbauer, Wesley Klewerton Guez Assunção and Alexander Egyed. “Comparison-Based Feature Location in ArgoUML Variants”.
Jamel Debbiche, Oskar Lignell, Jacob Krüger and Thorsten Berger. “Migrating Java-Based Apo-Games into a Composition-Based Software Product Line”.
Jonas Åkesson, Sebastian Nilsson, Jacob Krüger and Thorsten Berger. “Migrating the Android Apo-Games into an Annotation-Based Software Product Line”.


The SPLC challenge track aims at providing the software product-line (SPL) community with a set of case studies that tackle relevant SPL problems and challenge the state of the art. The challenge track was established with SPLC 2018 in Gothenburg, initiated by Sarah Nadi, Timo Kehrer, and Thorsten Berger.
The challenge is organized in two phases every year. The first phase is the call for cases. Submitted cases will be reviewed by the challenge co-chairs to ensure that all required information is clearly described. Accepted cases will be part of the official conference proceedings. Authors of the accepted cases must attend the challenge track and participate in the discussion. The second phase is a call for solutions to both newly accepted as well as previously accepted cases. Submitted case solutions will be peer-reviewed by the challenge program committee. Accepted solutions will also be part of the official conference proceedings. Authors of accepted solutions must present their papers during the conference.

You are highly encouraged to contribute to this website. For example by collecting references to challenge solutions outside the SPLC challenge track. You can propose any improvement or correction by direct editing the github-based website and creating a pull request , creating a github issue, or just sending an email to the challenge track co-chairs.

Challenge track co-chairs
Jabier Martinez, Tecnalia, Spain
Timo Kehrer, Humboldt-Universität zu Berlin, Germany


Applying Product Line Engineering Concepts to Deep Neural Networks

Javad Ghofrani, Ehsan Kozegar, Anna Lena Fehlhaber, and Mohammad Divband Soorati
Challenge and Solutions site
Deep Neural Networks (DNNs) are increasingly being used as a machine learning solution thanks to the complexity of their architecture and hyperparameters-weights. A drawback is the excessive demand for massive computational power during the training process. Not only as a whole but parts of neural networks can also be in charge of certain functionalities. We present a novel challenge in an intersection between machine learning and variability management communities to reuse modules of DNNs without further training. Let us assume that we are given a DNN for image processing that recognizes cats and dogs. By extracting a part of the network, without additional training a new DNN should be divisible with the functionality of recognizing only cats. Existing research in variability management can offer a foundation for a product line of DNNs composing the reusable functionalities. An ideal solution can be evaluated based on its speed, granularity of determined functionalities, and the support for adding variability to the network. The challenge is decomposed in three subchallenges: feature extraction, feature abstraction, and the implementation of a product line of DNNs.

Product Sampling for Product Lines: The Scalability Challenge

Tobias Pett, Thomas Thüm, Tobias Runge, Sebastian Krieter, Malte Lochau, and Ina Schaefer
Challenge and Solutions site
Quality assurance for product lines is often infeasible for each product separately. Instead, often only a subset of all products (i.e. a sample) is considered in testing such that at least the coverage of certain feature interactions is guaranteed. While pair-wise interaction sampling covers all interactions between two features, its generalization to t-wise interaction sampling ensures coverage for all interactions among t features. However, sampling for large product lines poses a challenge, as today’s algorithms tend to run out of memory, do not terminate, or produce samples, which are too large to be tested. To approach this challenge, we provide a set of large real-world feature-models with up-to 19 thousand features, which are supposed to be sampled. The performance of the sampling is evaluated based on the time and memory consumed to retrieve a sample and the sample size for a given coverage (i.e. t value). A well-performing sampling algorithm achieves full t-wise coverage, while minimizing all three of these properties.

Challenge track co-chairs
Sarah Nadi, University of Alberta, Canada
Timo Kehrer, Humboldt-Universität zu Berlin, Germany

Apo-Games – A Case Study for Reverse Engineering Variability from Cloned Java Variants

Jacob Krüger, Wolfram Fenske, Thomas Thüm, Dirk Aporius, Gunter Saake, and Thomas Leich
Challenge and Solutions site
Software-product-line engineering is an approach to systematically manage reusable software features and has been widely adopted in practice. Still, in most cases, organizations start with a single product that they clone and modify when new customer requirements arise (a.k.a. clone-and-own). With an increasing number of variants, maintenance can become challenging and organizations may consider migrating towards a software product line, which is referred to as extractive approach. While this is the most common approach in practice, techniques to extract variability from cloned variants still fall short in several regards. In particular, this accounts for the low accuracy of automated analyses and refactoring, our limited understanding of the costs involved, and the high manual effort. A main reason for these limitations is the lack of realistic case studies. To tackle this problem, we provide a set of cloned variants. In this paper, we characterize these variants and challenge the research community to apply techniques for reverse engineering feature models, feature location, code smell analysis, architecture recovery, and the migration towards a software product line. By evaluating solutions with the developer of these variants, we aim to contribute to a larger body of knowledge on this real-world case study.

Feature Location Benchmark with ArgoUML SPL

Jabier Martinez, Nicolas Ordoñez, Xhevahire Tërnava, Tewfik Ziadi, Jairo Aponte, Eduardo Figueiredo, and Marco Tulio Valente
Challenge and Solutions site
Feature location is a traceability recovery activity to identify the implementation elements associated to a characteristic of a system. Besides its relevance for software maintenance of a single system, feature location in a collection of systems received a lot of attention as a first step to re-engineer system variants (created through clone-and-own) into a Software Product Line (SPL). In this context, the objective is to unambiguously identify the boundaries of a feature inside a family of systems to later create reusable assets from these implementation elements. Among all the case studies in the SPL literature, variants derived from ArgoUML SPL stands out as the most used one. However, the use of different settings, or the omission of relevant information (e.g., the exact configurations of the variants or the way the metrics are calculated), makes it difficult to reproduce or benchmark the different feature location techniques even if the same ArgoUML SPL is used. With the objective to foster the research area on feature location, we provide a set of common scenarios using ArgoUML SPL and a set of utils to obtain metrics based on the results of existing and novel feature location techniques.

Interoperability of Software Product Line Variants

Ferruccio Damiani, Reiner Hähnle, Eduard Kamburjan, and Michael Lienhardt
Challenge and Solutions site
Software Product Lines are an established mechanism to describe multiple variants of one software product. Current approaches however, do not offer a mechanism to support the use of multiple variants from one product line in the same application. We experienced the need for such a mechanism in an industry project with German Railways where we do not merely model a highly variable system, but a system with highly variable subsystems. We present the design challenges that arise when software product lines have to support the use of multiple variants in the same application, in particular: How to reference multiple variants, how to manage multiple variants to avoid name clashes, and how to keep multiple variants interoperable.

Localizing Configurations in Highly-Configurable Systems

Paul Gazzillo, Ugur Koc, Thanhvu Nguyen, and Shiyi Wei
Challenge and Solutions site
The complexity of configurable systems has grown immensely, and it is only getting more complex. Such systems are a challenge for software testing and maintenance, because bugs and other defects can and do appear in any configuration. One common requirement for many development tasks is to identify the configurations that lead to a given defect or some other program behavior. We distill this requirement down to a challenge question: given a program location in a source file, what are valid configurations that include the location? The key obstacle is scalability. When there are thousands of configuration options, enumerating all combinations is exponential and infeasible. We provide a set of target programs of increasing difficulty and variations on the challenge question so that submitters of all experience levels can try out solutions. Our hope is to engage the community and stimulate new and interesting approaches to the problem of analyzing configurations.