As a model for knowledge description and formalization, ontologies are widely used to represent user profiles in personalized web
information gathering. However, when representing user profiles, many models have utilized only knowledge from either a global
knowledge base or user local information. In this paper, a personalized ontology model is proposed for knowledge representation
and reasoning over user profiles. This model learns ontological user profiles from both a world knowledge base and user local
instance repositories. The ontology model is evaluated by comparing it against benchmark models in web information gathering.
User profiles represent the concept models possessed by users when gathering web information. A concept model is implicitly
possessed by users and is generated from their background knowledge. While this concept model cannot be proven in laboratories,
many web ontologists have observed it in user behaviourThe results show that this ontology model is successful.