A personalized learning experience is possible with the use of learner models in intelligent tutoring systems. adaptive educational hypermedia systems and semantic web based learning environments. Although there are standards to overcome complexities or lack of fulfilling user needs (such as, IEEE or IMS), these models are either too generic or too complex to handle. In addition, there are various alternative learner or user models in the literature. Yet, these models do not address how to model learning object (LO) based instructional systems. Therefore, in this paper, an ontology based learner model is proposed for e-learning systems which use instructional learning objects.