1. An apparatus for extending a default model for user context reasoning, the apparatus comprising: a first generating unit configured to generate first relationship information about a relationship between a concept included in the default model and a concept included in a linked model by matching the concept of the default model with the concept of the linked model based on conception relationship information, the conception relationship information comprising at least one of information about identical concepts, information about similar concepts and information about upper and lower concepts; a second generating unit configured to generate second relationship information about a relationship between a concept included in the linked model and a concept included in linked data by matching the concept of the linked model with the concept of the linked data; and a combining unit configured to combine the default model and the linked model based on the first relationship information, and to combine the linked model and the linked data based on the second relationship information; and an internal memory located inside of the apparatus and configured to store the default model.