Yann-Gaël Guéhéneuc

Cristiano Politowski, Fabio Petrillo, João Eduardo Montandon et al.

Game engines help developers create video games and avoid duplication of code and effort, like frameworks for traditional software systems. In this paper, we explore open-source game engines along three perspectives: literature, code, and human. First, we explore and summarise the academic literature on game engines. Second, we compare the characteristics of the 282 most popular engines and the 282 most popular frameworks in GitHub. Finally, we survey 124 engine developers about their experience with the development of their engines. We report that: (1) Game engines are not well-studied in software-engineering research with few studies having engines as object of research. (2) Open-source game engines are slightly larger in terms of size and complexity and less popular and engaging than traditional frameworks. Their programming languages differ greatly from frameworks. Engine projects have shorter histories with less releases. (3) Developers perceive game engines as different from traditional frameworks. Generally, they build game engines to (a) better control the environment and source code, (b) learn about game engines, and (c) develop specific games. We conclude that open-source game engines have differences compared to traditional open-source frameworks although this differences do not demand special treatments.

Cristiano Politowski, Yann-Gaël Guéhéneuc, Fabio Petrillo

As the complexity and scope of game development increase, playtesting remains an essential activity to ensure the quality of video games. Yet, the manual, ad-hoc nature of playtesting gives space to improvements in the process. In this study, we investigate gaps between academic solutions in the literature for automated video game testing and the needs of video game developers in the industry. We performed a literature review on video game automated testing and applied an online survey with video game developers. The literature results show a rise in research topics related to automated video game testing. The survey results show that game developers are skeptical about using automated agents to test games. We conclude that there is a need for new testing approaches that did not disrupt the developer workflow. As for the researchers, the focus should be on the testing goal and testing oracle.

Gabriel C. Ullmann, Cristiano Politowski, Yann-Gaël Guéhéneuc et al.

Project Management anti-patterns are well-documented in the software-engineering literature, and studying them allows understanding their impacts on teams and projects. The video game development industry is known for its mismanagement practices, and therefore applying this knowledge would help improving game developers' productivity and well-being. In this paper, we map project management anti-patterns to anti-patterns reported by game developers in the gray literature. We read 440 postmortems problems, identified anti-pattern candidates, and related them with definitions from the software-engineering literature. We discovered that most anti-pattern candidates could be mapped to anti-patterns in the software-engineering literature, except for Feature Creep, Feature Cuts, Working on Multiple Projects, and Absent or Inadequate Tools. We discussed the impact of the unmapped candidates on the development process while also drawing a parallel between video games and traditional software development. Future works include validating the definitions of the candidates via survey with practitioners and also considering development anti-patterns.

João Eduardo Montandon, Cristiano Politowski, Luciana Lourdes Silva et al.

Context: There is a growing demand for information on how IT companies look for candidates to their open positions. Objective: This paper investigates which hard and soft skills are more required in IT companies by analyzing the description of 20,000 job opportunities. Method: We applied open card sorting to perform a high-level analysis on which types of hard skills are more requested. Further, we manually analyzed the most mentioned soft skills. Results: Programming languages are the most demanded hard skills. Communication, collaboration, and problem-solving are the most demanded soft skills. Conclusion: We recommend developers to organize their resumé according to the positions they are applying. We also highlight the importance of soft skills, as they appear in many job opportunities.

Cristiano Politowski, Lisandra Fontoura, Fabio Petrillo et al.

In the past 10 years, several researches studied video game development process who proposed approaches to improve the way how games are developed. These approaches usually adopt agile methodologies because of claims that traditional practices and the waterfall process are gone. However, are the "old days" really gone in the game industry? In this paper, we present a survey of software engineering processes in video game industry from postmortem project analyses. We analyzed 20 postmortems from Gamasutra Portal. We extracted their processes and modelled them through using the Business Process Model and Notation (BPMN). This work presents three main contributions. First, a postmortem analysis methodology to identify and extract project processes. Second, the study main result: \textbf{the "old days" are gone, but not completely}. \textbf{Iterative practices} are increasing and are applied to at least \textbf{65\% of projects} in which \textbf{45\% of this projects} explicitly adopted Agile practices. However, \textbf{waterfall} process is still applied at least \textbf{30\% of projects}. Finally, we discuss some implications, directions and opportunities for video game development community.

Cristiano Politowski, Lisandra M. Fontoura, Fabio Petrillo et al.

Context: The video game industry is a billion dollar industry that faces problems in the way games are developed. One method to address these problems is using developer aid tools, such as Recommendation Systems. These tools assist developers by generating recommendations to help them perform their tasks. Objective: This article describes a systematic approach to recommend development processes for video game projects, using postmortem knowledge extraction and a model of the context of the new project, in which "postmortems" are articles written by video game developers at the end of projects, summarizing the experience of their game development team. This approach aims to provide reflections about development processes used in the game industry as well as guidance to developers to choose the most adequate process according to the contexts they're in. Method: Our approach is divided in three separate phases: in the the first phase, we manually extracted the processes from the postmortems analysis; in the second one, we created a video game context and algorithm rules for recommendation; and finally in the third phase, we evaluated the recommended processes by using quantitative and qualitative metrics, game developers feedback, and a case study by interviewing a video game development team. Contributions: This article brings three main contributions. The first describes a database of developers' experiences extracted from postmortems in the form of development processes. The second defines the main attributes that a video game project contain, which it uses to define the contexts of the project. The third describes and evaluates a recommendation system for video game projects, which uses the contexts of the projects to identify similar projects and suggest a set of activities in the form of a process.

Cristiano Politowski, Fabio Petrillo, Gabriel C. Ullmann et al.

Context: Given its competitiveness, the video-game industry has a closed-source culture. Hence, little is known of the problems faced by game developers. However, game developers do share information about their games projects through postmortems, which describe informally what happened during the projects. Objective: The software-engineering research community and game developers would benefit from a state of the problems of the video game industry, in particular the problems faced by game developers, their evolution in time, and their root causes. This state of the practice would allow researchers and practitioners to work towards solving these problems. Method: We analyzed 200 postmortems from 1997 to 2019, resulting in 927 problems divided into 20 types. Through our analysis, we described the overall landscape of game industry problems in the past 23 years and how these problems evolved over the years. We also give details on the most common problems, their root causes, and possible solutions. We finally discuss suggestions for future projects. Results: We observe that (1) the game industry suffers from management and production problems in the same proportion; (2) management problems decreased over the years giving space to business problems, while production problems remained constant; (3a) technical and game design problems are decreasing over the years, the latter only after the last decade; (3b) problems related to the team increase over the last decade;(3c) marketing problems are the ones that had the biggest increase over the 23 years compared to other problem types; (4) finally, the majority of the main root causes are related to people, not technologies. Conclusions: In this paper we provide a state of the practice for researchers to understand and study video-game development problems. We also offer suggestions to help practitioners to avoid the most common problems.

Cristiano Politowski, Foutse Khomh, Simone Romano et al.

Context: Several studies investigated the impact of anti-patterns (i.e., "poor" solutions to recurring design problems) during maintenance activities and reported that anti-patterns significantly affect the developers' effort required to edit files. However, before developers edit files, they must understand the source code of the systems. This source code must be easy to understand by developers. Objective: In this work, we provide a complete assessment of the impact of two instances of two anti-patterns, Blob or Spaghetti Code, on program comprehension. Method: We analyze the impact of these two anti-patterns through three empirical studies conducted at Polytechnique Montréal (Canada) with 24 participants; at Carlton University (Canada) with 30 participants; and at University Basilicata (Italy) with 79 participants. Results: We collect data from 372 tasks obtained thanks to 133 different participants from the three universities. We use three metrics to assess the developers' comprehension of the source code: (1) the duration to complete each task; (2) their percentage of correct answers; and, (3) the NASA task load index for their effort. Conclusions: We report that, although single occurrences of Blob or Spaghetti code anti-patterns have little effect on code comprehension, two occurrences of either Blob or Spaghetti Code significantly increases the developers' time spent in their tasks, reduce their percentage of correct answers, and increase their effort. Hence, we recommend that developers act on both anti-patterns, which should be refactored out of the source code whenever possible. We also recommend further studies on combinations of anti-patterns rather than on single anti-patterns one at a time.

Cristiano Politowski, Fabio Petrillo, Gabriel Cavalheiro Ullmann et al.

Different from traditional software development, there is little information about the software-engineering process and techniques in video-game development. One popular way to share knowledge among the video-game developers' community is the publishing of postmortems, which are documents summarizing what happened during the video-game development project. However, these documents are written without formal structure and often providing disparate information. Through this paper, we provide developers and researchers with grounded dataset describing software-engineering problems in video-game development extracted from postmortems. We created the dataset using an iterative method through which we manually coded more than 200 postmortems spanning 20 years (1998 to 2018) and extracted 1,035 problems related to software engineering while maintaining traceability links to the postmortems. We grouped the problems in 20 different types. This dataset is useful to understand the problems faced by developers during video-game development, providing researchers and practitioners a starting point to study video-game development in the context of software engineering.

Antoine Barbez, Foutse Khomh, Yann-Gaël Guéhéneuc

Anti-patterns are poor solutions to recurring design problems. Number of empirical studies have highlighted the negative impact of anti-patterns on software maintenance which motivated the development of various detection techniques. Most of these approaches rely on structural metrics of software systems to identify affected components while others exploit historical information by analyzing co-changes occurring between code components. By relying solely on one aspect of software systems (i.e., structural or historical), existing approaches miss some precious information which limits their performances. In this paper, we propose CAME (Convolutional Analysis of code Metrics Evolution), a deep-learning based approach that relies on both structural and historical information to detect anti-patterns. Our approach exploits historical values of structural code metrics mined from version control systems and uses a Convolutional Neural Network classifier to infer the presence of anti-patterns from this information. We experiment our approach for the widely known God Class anti-pattern and evaluate its performances on three software systems. With the results of our study, we show that: (1) using historical values of source code metrics allows to increase the precision; (2) CAME outperforms existing static machine-learning classifiers; and (3) CAME outperforms existing detection tools.

Md Saidur Rahman, Emilio Rivera, Foutse Khomh et al.

SAP is the market leader in enterprise software offering an end-to-end suite of applications and services to enable their customers worldwide to operate their business. Especially, retail customers of SAP deal with millions of sales transactions for their day-to-day business. Transactions are created during retail sales at the point of sale (POS) terminals and then sent to some central servers for validations and other business operations. A considerable proportion of the retail transactions may have inconsistencies due to many technical and human errors. SAP provides an automated process for error detection but still requires a manual process by dedicated employees using workbench software for correction. However, manual corrections of these errors are time-consuming, labor-intensive, and may lead to further errors due to incorrect modifications. This is not only a performance overhead on the customers' business workflow but it also incurs high operational costs. Thus, automated detection and correction of transaction errors are very important regarding their potential business values and the improvement in the business workflow. In this paper, we present an industrial case study where we apply machine learning (ML) to automatically detect transaction errors and propose corrections. We identify and discuss the challenges that we faced during this collaborative research and development project, from three distinct perspectives: Software Engineering, Machine Learning, and industry-academia collaboration. We report on our experience and insights from the project with guidelines for the identified challenges. We believe that our findings and recommendations can help researchers and practitioners embarking into similar endeavors.

Hafedh Mili, Ghizlane El-Boussaidi, Anas Shatnawi et al.

Service-orientation views applications as orchestrations of independent software services that (1) implement functions that are reusable across many applications, (2) can be invoked remotely, and (3) are packaged to decouple potential callers from their implementation technology. As such, it enables organizations to develop quality applications faster than without services. Legacy applications are not service-oriented. Yet, they implement many reusable functions that could be exposed as \emph{services}. Organizations face three main issues when re-engineering legacy application to (re)use services: (1) to mine their existing applications for reusable functions that can become services, (2) to package those functions into services, and (3) to refactor legacy applications to invoke those services to ease future maintenance. In this paper, we explore these three issues and propose research directions to address them. We choose to focus on the service-oriented re-engineering of recent legacy object-oriented applications, and more specifically, on JEE applications, for several reasons. First, we wanted to focus on architectural challenges, and thus we choose to \textit{not} have to deal with programming language difference between source and target system. We chose JEE applications, in particular, because they embody the range of complexities that one can encounter in recent legacy applications, namely, multi-language systems, multi-tier applications, the reliance on external configuration files, and the reliance on frameworks and container services during runtime. These characteristics pose unique challenges for the three issues mentioned above.

Anas Shatnawi, Hafedh Mili, Manel Abdellatif et al.

Identifying dependency call graphs of multilanguage software systems using static code analysis is challenging. The different languages used in developing today's systems often have different lexical, syntactical, and semantic rules that make thorough analysis difficult. Also, they offer different modularization and dependency mechanisms, both within and between components. Finally, they promote and--or require varieties of frameworks offering different sets of services, which introduce hidden dependencies, invisible with current static code analysis approaches. In this paper, we identify five important challenges that static code analysis must overcome with multilanguage systems and we propose requirements to handle them. Then, we present solutions of these requirements to handle JEE applications, which combine server-side Java source code with a number of client-side Web dialects (e.g., JSP, JSF) while relying on frameworks (e.g., Web and EJB containers) that create hidden dependencies. Finally, we evaluate our implementations of the solutions by developing a set of tools to analyze JEE applications to build a dependency call graph and by applying these tools on two sample JEE applications. Our evaluation shows that our tools can solve the identified challenges and improve the recall in the identification of multilanguage dependencies compared to standard JEE static code analysis and, thus, indirectly that the proposed requirements are useful to build multilanguage static code analysis.

Rodrigo Morales, Ruben Saborido, Yann-Gaël Guéhéneuc

The Internet of Things (IoT) is a network of physical, heterogeneous, connected devices providing services through private networks and the Internet. It connects a range of new devices to the Internet so they can communicate with Web servers and other devices around the world. Today's standard platform for communicating Web pages and Web apps is JavaScript (JS) and extending the same standard platform to connect IoT devices seems more than appropriate. However, porting JS applications to the large variety of IoT devices, specifically on System-on-a-Chip (SoCs) devices (\eg~Arduino Uno, Particle \photon), is challenging because these devices are constrained in terms of memory and storage capacity. Running JS applications adds an overhead of resources to deploy a code interpreter on the devices. Also, running JS applications may not be possible ``as is'' on some device missing some hardware/software capabilities. To address this problem, we propose \momit~a multiobjective optimization approach to miniaturize JS applications to run on IoT constrained devices. To validate \momit, we miniaturize a JS interpreter to execute a testbed comprised of 23 applications and measure their performances before and after applying the miniaturization process. We implement \momit~using three different search algorithms and found that it can reduce code size, memory usage, and CPU time by median values of 31\%, 56\%, and 36\% respectively. Finally, MoMIT ported the miniaturized JS interpreters up to to 2 SoCs additional devices, in comparison of using default JS interpreter features.

Fabio Petrillo, Yann-Gaël Guéhéneuc, Marcelo Pimenta et al.

One of the most important tasks in software maintenance is debugging. To start an interactive debugging session, developers usually set breakpoints in an integrated development environment and navigate through different paths in their debuggers. We started our work by asking} what debugging information is useful to share among developers and study two pieces of information: breakpoints (and their locations) and sessions (debugging paths). To answer our question, we introduce the Swarm Debugging concept to frame the sharing of debugging information, the Swarm Debugging Infrastructure (SDI) with which practitioners and researchers can collect and share data about developers' interactive debugging sessions, and the Swarm Debugging Global View (GV) to display debugging paths. Using the SDI, we conducted a large study with professional developers to understand how developers set breakpoints. Using the GV, we also analyzed professional developers in two studies and collected data about their debugging sessions. Our observations and the answers to our research questions suggest that sharing and visualizing debugging data can support debugging activities.

Antoine Barbez, Foutse Khomh, Yann-Gaël Guéhéneuc

Anti-patterns are poor solutions to recurring design problems. Several empirical studies have highlighted their negative impact on program comprehension, maintainability, as well as fault-proneness. A variety of detection approaches have been proposed to identify their occurrences in source code. However, these approaches can identify only a subset of the occurrences and report large numbers of false positives and misses. Furthermore, a low agreement is generally observed among different approaches. Recent studies have shown the potential of machine-learning models to improve this situation. However, such algorithms require large sets of manually-produced training-data, which often limits their application in practice. In this paper, we present SMAD (SMart Aggregation of Anti-patterns Detectors), a machine-learning based ensemble method to aggregate various anti-patterns detection approaches on the basis of their internal detection rules. Thus, our method uses several detection tools to produce an improved prediction from a reasonable number of training examples. We implemented SMAD for the detection of two well known anti-patterns: God Class and Feature Envy. With the results of our experiments conducted on eight java projects, we show that: (1) our method clearly improves the so aggregated tools; (2) SMAD significantly outperforms other ensemble methods.

Anas Shatnawi, Hafedh Mili, Manel Abdellatif et al.

In this paper, we answer a set of research questions that are required to develop service identification approach based on the analysis of object- oriented software. Such research questions are: (1) what is a service, (2) how are services different from software components, (3) what are types of services, (4) what are existing service identification approaches that consider service types into account, and (5) how to identify services based on the object-oriented source code with respect to their types. Our methodology is based on performing a literature review to identify the answers of these research questions. Also, we propose a taxonomy of service types.

Anas Shatnawi, Hafedh Mili, Manel Abdellatif et al.

In this report, we propose our approach that identifies a KDM model of JSP pages. Our approach is based on two main steps. The first one aims to reduce the problem space by translating JSP pages into Java Servlets where we can use existing tools to identify a KDM model. The second step aims to complete the resulting KDM model by identifying dependencies of JSP tags that are not codified by the translation step.

Anas Shatnawi, Hafedh Mili, Manel Abdellatif et al.

In this paper, we propose a program slicing approach for the output stream object in JEE applications. Our approach is based on extracting a dependency call graph from KDM models of JEE applications. Then, it applies breath-first search algorithm to identify the program slice as a graph reachability problem. The proposed approach is implemented as an extension of our DeJEE tool.

Anas Shatnawi, Hafedh Mili, Manel Abdellatif et al.

Java Enterprise Edition (JEE) applications are implemented in terms of a set of components developed based on several JEE technologies includ- ing, but not limited to, Servlet, JSP, JSF, EJB, JavaBeans. These JEE technologies rely on a varied set of communication mechanisms to commu- nicate between each others. Examples of these communication mechanisms are HTTP requests, Remote Method Invocation (RMI), Java DateBase Connectivity (JDBC), etc. These communication mechanisms represent program dependencies between JEE components. However, one communi- cation mechanism can be implemented following different implementation ways by different JEE technologies. Therefore, to be able to detect related dependencies, we identify these implementation ways used by a set of JEE technologies. In this technical report, we focus on the Web tier technologies that are Servlets, JSPs and JSFs. Also, we present how these technologies access the JavaBeans and Manage Beans components.

Rubén Saborido, Foutse Khomh, Yann-Gaël Guéhéneuc et al.

The Android market is a place where developers offer paid and-or free apps to users. Free apps are interesting to users because they can try them immediately without incurring a monetary cost. However, free apps often have limited features and-or contain ads when compared to their paid counterparts. Thus, users may eventually need to pay to get additional features and-or remove ads. While paid apps have clear market values, their ads-supported versions are not entirely free because ads have an impact on performance. In this paper, first, we perform an exploratory study about ads-supported and paid apps to understand their differences in terms of implementation and development process. We analyze 40 Android apps and we observe that (i) ads-supported apps are preferred by users although paid apps have a better rating, (ii) developers do not usually offer a paid app without a corresponding free version, (iii) ads-supported apps usually have more releases and are released more often than their corresponding paid versions, (iv) there is no a clear strategy about the way developers set prices of paid apps, (v) paid apps do not usually include more functionalities than their corresponding ads-supported versions, (vi) developers do not always remove ad networks in paid versions of their ads-supported apps, and (vii) paid apps require less permissions than ads-supported apps. Second, we carry out an experimental study to compare the performance of ads-supported and paid apps and we propose four equations to estimate the cost of ads-supported apps. We obtain that (i) ads-supported apps use more resources than their corresponding paid versions with statistically significant differences and (ii) paid apps could be considered a most cost-effective choice for users because their cost can be amortized in a short period of time, depending on their usage.