Introduction to the special issue on search based software engineering

Search-based software engineering (SBSE) consists of the application of metaheuristic search techniques—such as genetic algorithms, simulated annealing, hill climbing, and tabu search—to software engineering problems. This idea is based on the observation that some software engineering activities can be thought of as optimization problems, and on the fact that techniques providing exact solutions are, very often, unable to adequately scale to large, real-world software engineering problems. Define fitness functions to guide an automated search for solutions, rather than attempting to construct solutions from scratch by hand. SBSE moves the engineer up the abstraction chain, from the tedious and expensive role of detailed solution construction, to the potentially more productive and more cost-effective area of fitness function design. This approach has been repeatedly demonstrated to have successful applications across the software engineering life cycle from requirements and project planning to maintenance and testing. This special issue focuses on applications of search SBSE to the maintenance phase of the life cycle. After software testing 2, software maintenance is the most widely studied application area for SBSE research. Work on SBSE applications to problems in software maintenance can be traced back to the pioneering work of the Mancoridis et al. 3, which led to the development of the Bunch tool for software re-modularization 4. In the past five years there has been a significant increase in SBSE applications to software maintenance and evolution. Search-based techniques have been applied to post-development code improvement problems, such as object-oriented refactoring 5, 6, and imperative language slicing and transformation 7. Other applications are related to software engineering economics and project management problems, such as release planning 8-12, effort, and cost estimation 13-16, and project staffing and planning 17-20. Last, but not the least, SBSE has been applied to deal with service-oriented architectures, for example for services QoS-aware composition 21, service-level agreement negotiation 22, and testing 23. A complete overview of SBSE with a discussion of future research trends can be found in the recent International Conference on Software Engineering (ICSE) ‘Future of Software Engineering’ paper 24. This issue of the Journal of Software Maintenance and Evolution: Research and Practice features three outstanding papers, dealing with different aspects of software maintenance and evolution: release planning and staffing, re-factoring, and component substitution. The paper ‘Optimized Staffing for Product Releases—Focused Search and its Application at Chartwell Technologies’ by Puneet Kapur, An Ngo-The, Günther Ruhe, and Andrew Smith presents an approach for optimizing the staffing for product releases. The problem they solve can be viewed as part of the more general release planning problem, which assigns features to releases such that technical, resource, risk, and budget constraints are met. In particular, the genetic search-based approach the authors propose aims at assigning human resources to software development tasks, taking them from a pool of developers having different levels of skills. The applicability of the proposed approach is demonstrated with an industrial case study. The paper ‘Search-Based Refactoring: an Empirical Study’ by Mark O'Keffe and Mel Ó Cinnéide presents an approach to automatically re-factor, using search-based techniques, object-oriented systems that undergo repeated addition of functionality. Such addition can, very often, deteriorate the quality of the system's underlying design. Their re-factoring is guided by the QMOOD quality model 25, and the paper compares different optimization techniques, such as Genetic Algorithms, Simulated Annealing, and Multiple Ascent Hill-Climbing. The results of experiments carried out on five software systems suggest that the latter technique outperforms the others. The paper ‘Search-based Many-to-one Component Substitution’ by Nicolas Desnos, Marianne Huchard, Guy Tremblay, Christelle Urtado, and Sylvain Vauttier presents a search-based approach that allows the replacement of an obsolete component with a composition of multiple components. When a component becomes obsolete, the approach searches for a minimal assembly of other components, exposing their functionality by means of ports that preserves the behavior of the original component. The proposed approach has been evaluated on a set of randomly generated components. We hope that readers will enjoy this special issue and find the selected papers insightful and inspiring. We would like to thank all the authors who presented papers for this special issue: there were many good quality papers, but unfortunately we could accept only three of them. Last, but not the least, we would like to thank the reviewers who provided timely, detailed and constructive feedbacks to the authors. Without their precious help this special issue would not have been possible.

Despite preceding related publications, works dealing with the resolution of software engineering problems by search techniques has especially risen since 2001. By its first decade, the Search Based Software Engineering (SBSE) approach has been successfully employed in several software engineering contexts, using various optimization techniques. Aside the relevance of such applications, knowledge regarding the publication patterns on the field plays an important role to its understanding and identity. Such information may also shed light into SBSE trends and future. This paper presents the first bibliometric analysis to SBSE publications. The study covered 740 publications of the SBSE community from 2001 through 2010. The performed bibliometric analysis concerned mainly in four categories: Publication, Sources, Authorship, and Collaboration. Additionally, estimates for the next years of several publication metrics are given. The study also analyzed the applicability of bibliometric laws in SBSE, such as Bradfords and Lotka.

Many software engineering problems are multi-objective in nature, which has been largely recognized by the Search-based Software Engineering (SBSE) community. In this regard, Pareto- based search algorithms, e.g., Non-dominated Sorting Genetic Algorithm II, have already shown good performance for solving multi-objective optimization problems. These algorithms produce Pareto fronts, where each Pareto front consists of a set of non- dominated solutions. Eventually, a user selects one or more of the solutions from a Pareto front for their specific problems. A key challenge of applying Pareto-based search algorithms is to select appropriate quality indicators, e.g., hypervolume, to assess the quality of Pareto fronts. Based on the results of an extended literature review, we found that the current literature and practice in SBSE lacks a practical guide for selecting quality indicators despite a large number of published SBSE works. In this direction, the paper presents a practical guide for the SBSE community to select quality indicators for assessing Pareto-based search algorithms in different software engineering contexts. The practical guide is derived from the following complementary theoretical and empirical methods: 1) key theoretical foundations of quality indicators; 2) evidence from an extended literature review; and 3) evidence collected from an extensive experiment that was conducted to evaluate eight quality indicators from four different categories with six Pareto-based search algorithms using three real industrial problems from two diverse domains.

This challenges and open problems paper discusses the role of software engineers when combining modeling with Search-Based Software Engineering (SBSE). With SBSE techniques increasingly providing insights into difficult software modeling problems, the role of the software engineer might be thought of as diminishing. However, given the crucial role of the model understanding in SBSE, we argue that the role of the software engineer will become more important through interactive SBSE, although exploiting this interaction remains a challenge for the field.

Search-Based Software Engineering (SBSE) researchers who apply multi-objective search algorithms (MOSAs) often assess the quality of solutions produced by MOSAs with one or more quality indicators (QIs). However, SBSE lacks evidence providing insights on commonly used QIs, especially about agreements among them and their relations with SBSE problems and applied MOSAs. Such evidence about QIs agreements is essential to understand relationships among QIs, identify redundant QIs, and consequently devise guidelines for SBSE researchers to select appropriate QIs for their specific contexts. To this end, we conducted an extensive empirical evaluation to provide insights on commonly used QIs in the context of SBSE, by studying agreements among QIs with and without considering differences of SBSE problems and MOSAs. In addition, by defining a systematic process based on three common ways of comparing MOSAs in SBSE, we present additional observations that were automatically produced based on the results of our empirical evaluation. These observations can be used by SBSE researchers to gain a better understanding of the commonly used QIs in SBSE, in particular, regarding their agreements. Finally, based on the results, we also provide a set of guidelines for SBSE researchers to select appropriate QIs for their particular context.

In the past five years there has been a dramatic increase in work on Search-Based Software Engineering (SBSE), an approach to Software Engineering (SE) in which Search-Based Optimization (SBO) algorithms are used to address problems in SE. SBSE has been applied to problems throughout the SE lifecycle, from requirements and project planning to maintenance and reengineering. The approach is attractive because it offers a suite of adaptive automated and semiautomated solutions in situations typified by large complex problem spaces with multiple competing and conflicting objectives. This article 1 provides a review and classification of literature on SBSE. The work identifies research trends and relationships between the techniques applied and the applications to which they have been applied and highlights gaps in the literature and avenues for further research.

Various software engineering paradigms and real-time projects have proved that software testing is the most critical and highly important phase in the SDLC. In general, software testing takes approximately 40–60% of the total effort and time involved in project development. Generating test cases is the most important process in software testing. There are many techniques involved in the automatic generation of these test cases which aim to find a smaller group of cases that could allow for an adequacy level to be achieved which will hence reduce the effort and cost involved in software testing. In the structural testing of a product, the auto-generation of test cases that are path focused in an efficient manner is a challenging process. These are often considered optimization problems and hence search-based methods such as genetic algorithm (GA) and swarm optimizations have been proposed to handle this issue. The significance of the study is to address the optimization problem of automatic test case generation in search-based software engineering. The proposed methodology aims to close the gap of genetic algorithms acquiring local minimum due to poor diversity. Here, dynamic adjustment of cross-over and mutation rate is achieved by calculating the individual measure of similarity and fitness and searching for the more global optimum. The proposed method is applied and experimented on a benchmark of five industrial projects. The results of the experiments have confirmed the efficiency of generating test cases that have optimum path coverage.

Declarative rules are frequently used in model refactoring in order to detect refactoring opportunities and to apply the appropriate ones. However, a large number of rules is required to obtain a complete specification of refactoring opportunities. Companies usually have accumulated examples of refactorings from past maintenance experiences. Based on these observations, we consider the model refactoring problem as a multi objective problem by suggesting refactoring sequences that aim to maximize both structural and textual similarity between a given model (the model to be refactored) and a set of poorly designed models in the base of examples (models that have undergone some refactorings) and minimize the structural similarity between a given model and a set of well‐designed models in the base of examples (models that do not need any refactoring). To this end, we use the Non‐dominated Sorting Genetic Algorithm (NSGA‐II) to find a set of representative Pareto optimal solutions that present the best trade‐off between structural and textual similarities of models. The validation results, based on 8 real world models taken from open‐source projects, confirm the effectiveness of our approach, yielding refactoring recommendations with an average correctness of over 80%. In addition, our approach outperforms 5 of the state‐of‐the‐art refactoring approaches.

Search-Based Software Engineering (SBSE) tools offer automatic support by applying search-based techniques to solve different optimization problems of various software engineering areas. However, configuring SBSE tools often requires expertise in optimization techniques, posing a significant barrier for non-specialist users. This task involves selecting suitable algorithms, tuning parameters, choosing appropriate objective functions and search operators, and making decisions that affect optimization quality and performance. To address this challenge, we propose a multiple-LLM approach that integrates Large Language Models (LLMs), specifically ChatGPT-4, into SBSEworkflows to provide context-aware and natural language suggestions for parameter configuration. The approach follows a Divide and Conquer strategy, in which specialized LLMs are trained for distinct parameter configuration subproblems. As a proof of concept, we implemented OPLA-Wizard that works with OPLA-Tool v2.0, for Product Line Architecture (PLA) design. This assistant supports users in configuring algorithm settings, search operators, and objective functions through a user-friendly interface. Preliminary results show that the multiple-LLM approach improves accuracy, explanation clarity, and output format adherence compared to a single-LLM approach. This work contributes to the democratization of SBSE by reducing cognitive load, preventing misconfigurations, and making advanced optimization techniques more accessible to a broader audience.

Software is an engineering material to be optimised. Until comparatively recently many computer scientists doubted this; why would one want to optimise something that could be made perfect by pure logical reasoning? However, the wider community has come to realise that, while very small programs may be perfect in isolation, larger software systems may never be (because the world in which they operate is not perfect). Once we accept this, we soon arrive at evolutionary computation as a means of optimising software. However, software is not merely some other engineering material to be optimised. Software is virtual and inherently adaptive, making it better suited to evolutionary computation than any other engineering material. This is leading to breakthroughs at the interface of software engineering and evolutionary computation, though there are still many exciting open problems for evolutionary commutation researchers to get their teeth into. This talk will cover some of these recent developments in Search Based Software Engineering (SBSE) and Dynamic Adaptive SBSE.

Big data driven genetic improvement for maintenance of legacy software systems

In Search-Based Software Engineering (SBSE), users typically select a set of Multi-Objective Search Algorithms (MOSAs) for their experiments without any justification, or they simply choose an MOSA because of its popularity (e.g., NSGA-II). On the other hand, users know certain characteristics of solutions they are interested in. Such characteristics are typically measured with Quality Indicators (QIs) that are commonly used to evaluate the quality of solutions produced by an MOSA. Consequently, these QIs are often employed to empirically evaluate a set of MOSAs for a particular search problem to find the best MOSA. Thus, to guide SBSE users in choosing an MOSA that represents the solutions measured by a specific QI they are interested in, we present an empirical evaluation with a set of SBSE problems to study the relationships among commonly used QIs and MOSAs in SBSE. Our aim, by studying such relationships, is to identify whether there are certain characteristics of a QI because of which it prefers a certain MOSA. Such preferences are then used to provide insights and suggestions to SBSE users in selecting an MOSA, given that they know which quality aspects of solutions they are looking for.

Search Based Software Engineering: Introduction to the Special Issue of the IEEE Transactions on Software Engineering

Software testing is a fundamental step in the software development lifecycle. Its purpose is to evaluate the quality of software applications. Regression testing is an important testing methodology in software testing. The purpose of regression testing is to validate the software after each change of its code. This involves adding new test cases to the test suite and running the test suite as the software changes, making the test suite larger. The cost and time of the project are affected by the test suite size. The challenge is to run regression testing with a smaller number of test cases and larger amount of software coverage. Minimization of the test suite with maximization of the software coverage is an NP-complete problem. Search-based software engineering is an important topic in software engineering, which addresses software engineering optimization problems to find the optimal/approximate solution of the given problem. This study investigated an approach to reducing the regression testing effort and saving time. It also solved the regression testing optimization problem by achieving the maximum test suite coverage with the minimum test suite size. Several experiments were conducted to obtain the optimal solutions for the regression testing problem. We propose an optimization methodology that combines a genetic algorithm and a greedy algorithm to optimize regression testing by respectively maximizing the software test coverage and minimizing the test suite size. The proposed methodology can conveniently deliver fault-free, fully covered, and powerful programs for mission-critical functions. It can be applied to test a real-time system that has high requirements for reliability, security, and safety.

A critical concept in requirements engineering is a requirement. The requirements work is to answer this question: “What do you want to achieve in a product or service?”, Which is simple to say, but not necessarily very easy in practice. Analysis and management of dependencies among needs is a critical area of requirements engineering. The purpose of the research in the field of search-based software engineering is transfer of software engineering issues from a search based on human activities to a machine-based search using methods such as Meta heuristic search, evolutionary computation paradigms, and operations research. The main idea is to exploit the creativity of humans and the reliability of machines instead of using humans that are prone to engineering error and time consuming. In this article, we will categorize the existing approaches and focus on the third category.