additional explanations:
hide from the user some parts of information about a particular concept which are not relevant to the user's level of knowledge about this concept.
prerequisite explanations and comparative explanations:
Change the information presented about a concept depending on the user knowledge level of related concepts.
The first method is based on prerequisite links between concepts.
The second method is based on similarity links between concepts.
explanation variants:
Storing variants for some parts of the page content and the user gets the variant corresponds to his or her user model.
sorting:
sorting the fragments of information and placing toward the front according to relevance to user's background and knowledge is .