1. A context aware apparatus comprising: an extracting processor configured to extract, from a semantic model, a terminological-box (T-box) comprising information that defines a relationship between classes; a first generating processor configured to generate a reasoning rule based on the extracted T-box; a second generating processor configured to generate a first assertion-box (A-box) based on sensing information, wherein the sensing information relates to information sensed to recognize a user state; and a reasoning processor configured to infer a user context based on the reasoning rule and the first A-box.