Information retrieval has a well-established tradition of performing laboratory experiments on test collections to compare the relative effectiveness of different retrieval approaches. The experimental design specifies the evaluation criterion to be used to determine if one approach is better than another. Retrieval behavior is sufficiently complex to be difficult to summarize in one number, many different effectiveness measures have been proposed. A concept model is implicitly possessed by users and is generated from their background knowledge. 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. The results show that this ontology model is successful.