Context resources that users and sensors have within an area are heterogeneous in structure, so they are insufficient for monitoring the situation of moving users. In addition, portable mobile devices usually have a limited processing capacity for processing a large volume of context resources. The present study defines context structure for recognizing dynamic changes in users' environment and proposes a model for processing users' situation. The proposed context structure distinguishes between dynamic and static contexts according to the volume of context change, and defines correlations among objects. Therefore, users' situation can be inferred using ontology.