## 8 Conclusions  
In this research, a framework to realize, twin, and analyze the IFC-based 4D construction management information model of prefabricated buildings is proposed and validated with a construction project. The IFC-based framework is proposed to fill the gap that the IFC standard has difficulties in construction management information's interoperability and automated analysis. This framework achieves four objectives: (1) A unified IFC-based construction management information model is established to integrate the construction management information needed in the construction process. It provides a feasible solution for managing the whole process of prefabricated building construction using a unified information model. (2) The algorithm to twinning the IFC-based 4D construction management information model into the graph database-based information model is designed. In this approach, IFC-based construction management information can be interoperated among different stakeholders, construction stages, and different BIM software. Furthermore, it lays the foundation of automated analysis of the graph-based information model. (3) The strategies to automatically analyze the schedule networks and analyze the delay are proposed. On the one hand, the analysis of the IFC-based and graph database-based construction management information model can identify the tasks' centrality in the schedule network and then determine the tasks' delay, which can help the managers control the construction process. On the other hand, the analysis of the construction schedule provides the necessary knowledge preparation for in-depth analysis and management of the construction process based on IFC and graphical databases. (4) The means to visualize the IFC-based 4D information model is given. Thus, the IFC-based information model can have a dynamic 4D presentation and visualize the results of construction schedules' analysis. In general, the contributions of this framework to the development of prefabricated buildings' construction management are twofold. Firstly, this framework can promote the IFC-based construction management of prefabricated buildings by achieving the construction information's interoperability, which is difficult to achieve in the current construction information management of prefabricated buildings. Secondly, this framework can enhance the managers' control of processes by automatically analyzing construction schedules and visualizing the construction management information model based on graph database. This has greatly improved the efficiency of the CPM method, which used to have a time lag and be calculated manually. Based on the results of this paper, related work can be further carried out. This research's further works include: (1) Limited by BIM software functions, the resource information in the IFC-based 4D construction management information model cannot be well displayed. Further work can be the secondary development of relevant BIM software to realize the display of resource information. (2) In this extended information model, only prefabricated components are considered. More efforts are needed to include the cast-in-situ sections that have a more complicated construction process. (3) The graph and its parameters obtained based on the IFC twins can be further applied in the graph neural networks (GNN) to help the research on the efficiency improvement of the building construction process. (4) The framework developed in this paper can be extended to the scope of project life-cycle management and be the digital foundation of the energy consumption management during building operations and maintenance. **Author Contributions:** Conceptualization, B.Y. ; methodology, M.D., C.W. and B.L. ; software, M.D. ; writing--original draft preparation, M.D. ; writing--review and editing, Z.W. and B.Z. ; supervision, B.Y. All authors have read and agreed to the published version of the manuscript. This study is supported by the National Key R&D Program of China (Grant No. 2018 YED1100900).