This paper presents a stereotype-based user model for adaptive hypermedia s
ystems. We use a suitable algebraic fuzzy structure which can adequately re
flect some features of the user in the model, and apply this model to adapt
the navigation and the content of hypermedia nodes to the user's needs. Th
e model includes temporal representations of the user and approximates ever
y real user by a set of stereotypes, from which the one realizing the best
approximation earn always be extracted. The set of stereotypes is the suppo
rt set of the structure and the operations defined therein may be supplied
with adequate semantics which allow for the selection of the stereotype.