The focus of the paper is to reveal the relationships between software maintainability and other internal software quality attributes. The source code characteristics of five Java-based open-source software products are analyzed using the software measurement tool SoftCalc. The relationships between maintainability and internal quality attributes are identified based on the Pearson product moment correlation analysis. Our results show negative correlations between maintainability and some well-known internal software quality attributes, as well as the ones between maintainability and complexity metrics. Particularly, according to our results, the Number of Data Variables Declared and the Decisional Complexity McClure Metric have the strongest correlations with maintainability. The results of our study, that is to say, knowledge about the relationships between internal software quality attributes and maintainability, can be used as a basis for improvement of software maintainability at earlier stages of the software development process. Copyright ASSESSING MAINTAINABILITY CHANGE OVER MULTIPLE SOFTWARE RELEASES 33 RESEARCH BACKGROUNDThis section highlights the most important background studies carried out by other researchers that are related to our topic. First, we focus on those studies that analyze the relationships between maintainability and internal quality attributes, since this is the primary focus of our paper. Second, we present the studies that scrutinize the relationships between software complexity metrics and maintenance. In fact, software complexity metrics are considered to be internal quality attributes, but we decided to present them in a separate section because of their importance and wide practical usage. Third, some studies on maintainability measurement have been taken into account, since the maintainability measurement model used in our study differs from the previous models developed by other researchers. Finally, owing to the fact that our study is based on analysis of multiple software releases over time, some studies on the relationships between software evolution and source code changes have been discussed. Relationship between internal quality attributes and maintenanceBy measuring adaptive maintenance effort (AME), Fioravanti and Nesi [12] analyzed how various metrics related to AME change over multiple system versions (releases). By considering a system with seven versions, Fioravanti and Nesi found out that Class Complexity (CC), Number of Attributes and Methods of a Class (NAM) and Class Method Interface Complexity Local (CMICL) tend to increase considerably over time. Their values increase ca. 7-8 times over six releases. Class Attribute Complexity Inherited (CACI), Class Attribute Complexity Local (CACL) and Class Method Interface Complexity Inherited (CMICI) were also found to have a growing trend over time. However, this trend is not as considerable as in the case of CC and NAM: the metric values grow only ca. 2.5 times.In our study we are going to analyze the internal quality ...

The paper presents a model for the analysis, comparison and validation of standards, specifications and in particular reference models in the field of Technology Enhanced Learning (TEL). The Reference Model Analysis Grid (RMAG) establishes categories of reference models and standards. Based on those categories, a set of criteria for the analysis and validation of standards was elaborated as a part of the ICOPER project that aims at interoperable open content for competency-based TEL. The analysis of standards in this context is targeted at developing a set of validated approaches that lead to a new reference model. Four standards were investigated, taking into account a broad range of aspects like practical and semantic interoperability and integration issues. In the case study, the authors analyzed both, the standards and specifications and the usefulness of the RMAG. The results of this case study can be used for further analyses of TEL standards as well as for reference models targeted at interoperability.

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The goal of this study is to explore how fault-proneness of open source software (OSS) could be explained in terms of internal quality attributes and maintenance process metrics. We reviewed earlier studies and performed a multiple case study of eight Java-based projects based on data available in the Source Forge repository. Overall, we studied 342 releases of those systems. As is usual, software quality was regarded as a set of internal and external quality attributes. A total of 76 internal quality attributes were measured from the source code of the selected systems via the tool SoftCalc. Two external quality attributes contributing to fault-proneness were in turn obtained from the Source Forge Issue Tracking System. The framework for assessing the maintenance process was adopted from our previous studies. Its distinguishing feature is that it takes into account the peculiarities of OSS development. We included 23 maintenance process metrics to this study. Relationships between the metrics under study were identified by means of correlation analysis, multiple regression analysis and factor analysis. The obtained results give an interesting insight into interpretation of the earlier results of other researchers, regarding especially their generalizability. The strengths of our study include the following: 1) we studied a greater number of metrics than most of the related studies, 2) we studied a greater number of OSS-systems than most of the studies, and 3) we focused on the fault-proneness of modern Java-based systems and investigated them as an aggregated sample.

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