Cognitive Tutor Authoring Tools software. As of version 2.1, CTAT logs to the format described in this document.

Document Type Definition. The rules describing the structure of a class of XML markup. In the PSLC community, the "tutor message DTD" is a reference to the logging format described in this document. Going forward, "XML Schema", a successfor to DTD, will be used by the PSLC to define the tutor message format.

Carnegie Mellon's Online Learning Initiative, a project that specializes in creating online education and courses based on "cognitive theory, formative evaluation for students and faculty, and iterative course improvement based on empirical evidence" (http://www.cmu.edu/oli/overview/index.html). Its software is the deployment platform for PSLC courses and studies.

Selection, action, input triple. Format for referring to a component of a user interface (selection), the action performed on it (action), and the student input into that component (input).

An instance of student use of the tutor, initiated by student log-in into a system.

An XML language used to describe the rules governing the structure and content of an XML document. The tutor message format is described by an XML Schema document (an XSD), which replaces the DTD.