The Industry Foundation Classes (IFC) has been known as a common product model that has interoperability between similar and dissimilar IT systems for the architecture, engineering, construction, and facility management (AEC/FM) industries covering all life cycle phases. Continuous efforts have been undertaken regarding the development of standardized specifications based on the IFC, a product model used in the AEC/FM industries. In accordance, the XM-4 project has been initiated by the Korea Chapter of the International Alliance for Interoperability (IAI) organizations to develop a two-dimensional (2D) extension model for IFC. The XM-4 project aims to add to the IFC2x platform the ability to exchange 2D computer-aided design data within representations of virtual building models, including annotations and styles mainly adapted from the ISO 10303. The focus of this research has been on developing a 2D extension model for the IFC as part of the IAI XM-4 project. This paper provides the scope and rationale of the model extension, major modeling concepts, defined high-level entities and row-level entities, and implementation issues to be considered.
