Visualizing impacts of database schema changes - A controlled experiment

Research in schema evolution has been driven by the need for more effective software development and maintenance. Finding impacts of schema changes on the applications and presenting them in an appropriate way are particularly challenging. We have developed a tool that finds impacts of schema changes on applications in object-oriented systems. This tool displays components (packages, classes, interfaces, methods and fields) of a database application system as a graph. Components potentially affected by a change are indicated by changing the shape of the boxes representing those components. Two versions of the tool are available. One version identifies affected parts of applications at the granularity of packages, classes, and interfaces, whereas the other version identifies affected parts at the finer granularity of fields and methods. This paper presents the design and results of a controlled student experiment testing these two granularity levels with respect to productivity and user satisfaction. There are indications that identifying impacts at the finer granularity can reduce the time needed to conduct schema changes and reduce the number of errors. Our results also show that the subjects of the experiment appreciated the idea of visualizing the impacts of schema changes.