The Unified Modeling Language (UML) provides various diagram types for describing a system from different perspectives or abstraction levels. Hence, UML diagrams describing the same system are dependent and strongly overlapping. In this paper we study how this can be exploited for specifying transformation operations between different diagram types. We discuss various general approaches and viewpoints of model transformations in UML. The source and target diagram types for useful transformations are analyzed and given categories. The potentially most interesting transformation operations are discussed in detail. It is concluded that the transformation operations can automate a substantial part of both forward and reverse engineering. These operations can be used, for example, for model checking, merging, slicing, and synthesis.

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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 ...

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