Another technique is the usage of topic maps, as used in EON, an authoring tool for Pedagogy-Oriented Intelligent Tutors [7]. There are different types of nodes, links and properties of the same. Different shapes are used to represent factual, conceptual and procedural knowledge. Properties of topics include importance and difficulty. Topic link types include
”prerequisite”, ”part-of”, ”is-a” and ”context-for”. They are stored in XML format.