A systematic literature review of machine learning techniques for software maintainability prediction

Context: Software maintainability is one of the fundamental quality attributes of software engineering. The accurate prediction of software maintainability is a significant challenge for the effective management of the software maintenance process. Objective: The major aim of this paper is to present a systematic review of studies related to the prediction of maintainability of object-oriented software systems using machine learning techniques. This review identifies and investigates a number of research questions to comprehensively summarize, analyse and discuss various viewpoints concerning software maintainability measurements, metrics, datasets, evaluation measures, individual models and ensemble models. Method: The review uses the standard systematic literature review method applied to the most common computer science digital database libraries from January 1991 to July 2018. Results: We survey 56 relevant studies in 35 journals and 21 conference proceedings. The results indicate that there is relatively little activity in the area of software maintainability prediction compared with other software quality attributes. CHANGE maintenance effort and the maintainability index were the most commonly used software measurements (dependent variables) employed in the selected primary studies, and most made use of class-level product metrics as the independent variables. Several private datasets were used in the selected studies, and there is a growing demand to publish datasets publicly. Most studies focused on regression problems and performed k-fold cross-validation. Individual prediction models were employed in the majority of studies, while ensemble models relatively rarely. Conclusion: Based on the findings obtained in this systematic literature review, ensemble models demonstrated increased accuracy prediction over individual models, and have been shown to be useful models in predicting software maintainability. However, their application is relatively rare and there is a need to apply these, and other models to an extensive variety of datasets with the aim of improving the accuracy and consistency of results

The performance of some machine learning approaches and a rich context model in student answer prediction

Web-based learning systems with adaptive capabilities to personalize content are becoming nowadays a trend in order to offer interactive learning materials to cope with a wide diversity of students attending online education. Learners’ interaction and study practice (quizzing, reading, exams) can be analyzed in order to get some insights into the student’s learning style, study schedule, knowledge, and performance. Quizzing might be used to help to create individualized/personalized spaced repetition algorithm in order to improve long-term retention of knowledge and provide efficient learning in online learning platforms. Current spaced repetition algorithms have pre-defined repetition rules and parameters that might not be a good fit for students’ different learning styles in online platforms. This study uses different machine learning models and a rich context model to analyze quizzing and reading records from e-learning platform called Hypocampus in order to get some insights into the relevant features to predict learning outcome (quiz answers). By knowing the answer correctness, a learning system might be able to recommend personalized repetitive schedule for questions with maximizing long-term memory retention. Study results show that question difficulty level and incorrectly answered previous questions are useful features to predict the correctness of student’s answer. The gradient-boosted tree and XGBoost models are best in predicting the correctness of the student’s answer before answering a quiz. Additionally, some non-linear relationship was found between the reading learning material behavior in the platform and quiz performance that brings added value to the accuracy for all used models

Correlating Working Memory Capacity with Learners´ Study Behavior in a Web-Based Learning Platform

Cognitive pre-requisites should be taken into consideration when providing personalized and adaptive digital content in web-based learning platforms. In order to achieve this it should be possible to extract these cognitive characteristics based on students´ study behavior. Working memory capacity (WMC) is one of the cognitive characteristics that affect students’ performance and their academic achievements. However, traditional approaches to measuring WMC are cognitively demanding and time consuming. In order to simplify these measures, Chang et al. (2015) proposed an approach that can automatically identify students’ WMC based on their study behavior patterns. The intriguing question is then whether there are study behavior characteristics that correspond to the students’ WMC? This work explores to what extent it is possible to map individual WMC data onto individual patterns of learning by correlating working memory capacity with learners´ study behavior in an adaptive web-based learning system. Several machine learning models together with a rich context model have been applied to identify the most relevant study behavior characteristics and to predict students’ WMC. The evaluation was performed based on data collected from 122 students during a period of 2 years using a web-based learning platform. The initial results show that there is no linear correlation with learners´ study behavior and their WMC

Applications of metal foam as catalyst carrier

Catalytic processes are used in a wide range of applications, e.g. in automotive, chemical industry, combustion processes and power generation. Open cell metallic foams with their specific structural properties are attractive candidates for catalyst supports. Their high porosity and irregular structure ensure an intensive gas reaction with the catalytic surface. The foam can be produced in a wide range of pure metals like nickel, iron, silver, copper by an electroplating process. For high temperature operation conditions the metallic foam substrates can be alloyed by a patented powder metallurgical process in industrial scale e.g. to NiCrAl and NiFeCrAl foams which have a high strength and oxidation resistance over the life time. In this paper results from the past research will show the potential of metallic foams for applications in heterogeneous catalyses and biogas desulfurization