IFCdiff : A content-based automatic comparison approach for IFC files

With the growth in popularity of the IFC (Industry Foundation Classes) format used in construction industry, it often requires effective methods of IFC comparison to keep track of important changes during the lifecycle of construction projects. However, most IFC comparisons are based on a visual inspection, a manual count and a check of selective attributes. Although a few techniques about automatic IFC comparisons have been developed recently, they are usually time-consuming, and are sensitive to the GUID change or redundant instances in IFC files. To address these issues, we propose a content-based automatic comparison approach, named IFCdiff, for detecting differences between two IFC files. The proposed approach starts with a comprehensive analysis of the structure and content of each IFC file, and then constructs its hierarchical structure along with eliminating redundant instances. Next, the two hierarchical structures are compared with each other for detecting changes in an iterative bottom-up procedure. Our approach fully considers the content of IFC files without the need of flattening instances in IFC files. In contrast with previous methods, our approach can greatly reduce the computational time and space, and the comparison result is not sensitive to redundant instances in IFC files. Finally, we demonstrate a potential application to incremental backup of IFC files. The software can be found at: http://cgcad.thss.tsinghua.edu.cn/liuyushen/ifcdiff/.