Enhanced Visualization of Method Invocations by Extending Reverse-engineered Sequence Diagrams

Software maintainers employ reverse-engineered sequence diagrams to visually understand software behavior, especially when software documentation is absent or outdated. Much research has studied the adoption of reverse-engineered sequence diagrams to visualize program interactions. However, due to the forward-engineering nature of sequence diagrams, visualizing more complex programming scenarios can be challenging. In particular, sequence diagrams represent method invocations as unidirectional arrows. However, in practice, source code may contain compound method invocations that share values/objects implicitly. For example, method invocations can be nested, e.g., fun (foo ()), or chained, e.g., fun (). foo (). The standard notation of sequence diagrams does not have enough expressive power to precisely represent compound scenarios of method invocations. Understanding the flow of information between method invocations simplifies debugging, inspection, and exception handling operations for software maintainers. Despite the research invested to address the limitations of UML sequence diagrams, previous approaches fail to visualize compound scenarios of method invocations. In this paper, we propose sequence diagram extensions to enhance the visualization of (i) three widely used types of compound method invocations in practice (i.e., nested, chained, and recursive) and (ii) lifelines of objects returned from method invocations. We aim through our extensions to increase the level of abstraction and expressiveness of method invocation code. We develop a tool to reverse engineer compound method invocations and generate the corresponding extended sequence diagrams. We evaluate how our proposed extensions can improve the understandability of program interactions using a controlled experiment. We find that program interactions are significantly more comprehensible when visualized using our extensions.