A systematic approach to analyzing voting terminal event logs

This paper presents a systematic approach to automating the analysis of event logs recorded by the electronic voting tabulators in the course of an election. An attribute context-free grammar is used to specify the language of the event logs, and to distinguish compliant event logs (those that adhere to the defined proper conduct of an election) and non-compliant logs (those that deviate from the expected sequence of events). The attributes provide additional means for semantic analysis of the event logs by enforcing constraints on the timing of events and repetitions of events. The system is implemented with the help of commodity tools for lexical analysis and parsing of the logs. The system was rigorously tested against several thousand event logs collected in real elections in the State of Connecticut. The approach based on an attribute grammar proved to be superior to a previous approach that used state machine specifications. The new system is substantially easier to refine and maintain due to the very intuitive top-down specification. An unexpected benefit is the discovery of revealing and previously unknown deficiencies and defects in the event log recording systems of a widely used optical scan tabulator.