This chapter describes a theoretical rationale and an empirical methodology for analysing log-file data recorded from students' interactions with computer-based problem-solving assessment tasks. These analyses can play an important role in the development and refinement of rules for automatically scoring complicated sequences of process data which describe procedural aspects of problem solving. It presents examples of log files and analyses from an interactive problem-solving task. In complex domains where a variety of skills and dispositions may influence performance, interpreting log-file data to infer how students solve problems could provide valid information to help meet their instructional needs. [Author abstract]