Answering program understanding questions on demand with task-specific runtime information

When debugging or otherwise understanding software, developers frequently ask questions such as “how did this function get called?” and “where did this value come from?”. Runtime data is a valuable yet underused resource for answering these questions. There are at least four major barriers to answering questions with runtime data: 1) Deciding what runtime data should be collected 2) Deciding how to collect relevant runtime data 3) Aggregating and summarizing collected data 4) Interpreting the results to make conclusions.