VanLehn, K. & Garlick, S. (1987). Cirrus: an automated protocol analysis tool. In P. Langley(Ed.),Proceedings of the Fourth International Workshop on Machine Learning, 205-217. Los Altos, CA: Morgan Kaufmann.

Cirrus is a tool for protocol analysis. Given an encoded protocol of a subject solving problems, it constructs a model that will produce the same protocol as the subject when it is applied to the same problems. In order to parameterize Cirrus for a task domain, the user must supply it with a problem space: a vocabulary of attributes and values for describing spaces, a set of primitive operators, and a set of macro-operators. Cirrus' model of the subject is a hierarchical plan that is designed to be executed by an agenda-based plan follower. Cirrus' main components are a plan recognizer and a condition inducer. The condition inducer is based on Quinlan's ID3. Cirrus has potential applications not only in psychology but also as the student modelling component in an intelligent tutoring system.

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