Sequential debugging at a high level of abstraction

Efforts to build a better mousetrap for bugs in sequential programs are described. The resulting debugger, called Dalek, is intended to remedy limitations in conventional execution harnesses. Beyond the simple 'stop and look' features offered by typical breakpoint debuggers, Dalek offers a rich control and query language. Dalek's linguistic capabilities for treating sequences of program events offer an improvement over scratch paper as a compensatory technology for human memory limitations. Example applications are given. The very interactive, dynamic style of debugging encouraged by Dalek is discussed.>