Graph-based version control for asynchronous BIM level 3 collaboration

Collaboration and communication are two essential aspects of Building Information Modeling (BIM). Current standards such as ISO 19650 take this into account by propagating the concept of federated domain models based on file-based information containers (BIM level 2). In consequence, complete models are transmitted every time a new version is shared with the collaborators. As changes in domain models cannot be tracked for individual objects, but for whole files only, high effort for the subsequent coordination across the domains is created. These limitations can be overcome by implementing modern approaches of digital collaboration based on object-level synchronization, as denoted as BIM level 3. To provide a methodological basis, this paper proposes to represent the object-networks of BIM models as formal graphs and describing changes in the model as graph transformations. Consequently, modifications can be transmitted as patches using the graph formalisms, which are to be integrated and interpreted on the receiving side, thus achieving object-level synchronization. The paper discusses in detail the graph-based representation and the implementation of the necessary graph comparison algorithms.