Thresholds for Software Quality Metrics in Open Source Android Projects

Quality is an important aspect of every software development project. Different stakeholders are interested in different aspect of quality. For instance, from the users point of view, it represents to what extent the application is satisfying their needs. On the other hand, developers may be more interested in the efforts needed to fix bugs, testing, extending existing functionalists provided by the application and adding new ones. One aspect of measuring and ensuring quality can be achieved by utilizing software metrics. Multiple metrics suites have been proposed and they all capture different aspects of quality. Product metrics, can reveal internal characteristics of an application and help developers to reach better quality. They indicate how maintainable, testable and extendable one application is based on inheritance characteristics, size and complexity of the applications modules. Since the metrics are represented by a number only and the guidelines for each metric specify the desired value, we need thresholds that will define the lower and upper limit for each metric i.e., reference values that developers can relate to. Five metrics, including Number Of Methods, Response For Class, Depth of Inheritance Tree, Number Of Children and Coupling Between Objects were successfully computed for 865 Android applications. By calculating the metrics on large number of applications, thresholds for 17 categories of applications have been proposed. These thresholds are different depending what category does the application belong to system, games, multimedia, etc. In addition, each category was divided into subcategories based on size and thresholds were proposed for the appropriate subcategories. By sub-categorizing we allow developers to have a reference values for their applications based on the size in addition to categor