Abstract
New technologies create possibilities for the appreciation of e-learning content to a larger audience. While the number of challenges in the application of these technologies is still considerable, their potential justifies the effort required for their application. These technologies can provide an intelligent nature for e-learning systems and facilitate the adaptation/personalization of learning content and learning tasks. This intelligent or adaptive nature can be provided by relying on what is usually called user models. Researchers in the e-learning community have always considered it important to develop a model of the learner that contains important information that can be used to adapt the system according to learners' needs. Surprisingly, most of the existing proposed user models are not comprehensive enough and lack many features. More research should be devoted to develop a comprehensive user model to assure the gain of the most benefits of adaptation. At present, most adaptive systems use local user models and are not able to deal with external user models. Moreover, existing user models neglect an explicit support for information imperfection and prevent users from editing their own information. In this paper, we present a flexible and comprehensive multi-layer user model based on the IMS Learner Information Package (LIP) standard to assure interoperability and reusability across different e-learning systems.