## 3 Methodology  
This paper develops a framework consisting of three parts to realize the interoperability and automated analysis of prefabricated buildings' construction management information, as Figure 1 shows. In this figure, we can explicitly find the framework is divided into four layers, namely, Data Acquisition Layer, Realization Layer, Interoperability Layer, and Analysis Layer. Data Acquisition Layer gleans fabrication information, transport information, hoisting information, and installation information of construction process. The Realization Layer realizes an IFC-based 4D construction management information model of prefabricated buildings. After twinning the obtained information model into the graph database, the Interoperability Layer is the platform for data interoperation. The Analysis Layer is based on the IFC and graph database and has the function of data update, schedule network analysis, delay analysis and 4D visualization. Firstly, this framework realizes an IFC-based 4D construction management information model of prefabricated buildings. Through this part, the construction management information needed in the construction process is integrated into a unified information model, and thus lays the foundation for the information management of prefabricated buildings' construction process. The establishing procedure is divided into two steps. The first step is extending the IFC schema. An integrated prefabricated buildings' construction management information model is established in this step, including task information and related component information, resource information, cost information, and schedule analysis information. The second step is to instantiate the template one-by-one according to the obtained construction information to complete the IFC-based 4D construction management information model of prefabricated buildings. The detailed creation process is shown in Section 4. Furthermore, this framework twins the obtained IFC-based 4D construction management information model into the graph database. Through this part, the IFC-based construction management information model can be well interoperated among different participants and facilitates the construction analysis in the following part at the same time. The information model obtained in the previous parts of the framework is based on the IFC standard, which has high structural complexity and low data density [45]. These features lead the IFC-based information model to have difficulties in reading, retrieve, and interop  
Figure 1: Framework overview. eration. This framework introduces a non-relationship database--graph database--to solve the problem; first, by formulating the mapping rules and twin the IFC-based construction management into a task-centered network. In this network, all the relationships between tasks, resources, costs, components, and schedule analysis information can be obtained and used, making the IFC-based information retrieved and read easily. Secondly, all the participants can operate the database to update the construction information. This information will be transmitted to other participants timely, making the interoperation among stakeholders and different construction stages efficient. Finally, IFC files are outputted from the graph database by traversing the graph database's information, thus achieving the round-tripping between the graph database-based information network and the IFC-based 4D information model. The detailed creation mechanism is shown in Section 5. The last part of this framework is strategies to analyze the graph database-based information model. Through this part, the framework based on IFC realizes the data update, automatic analysis, and dynamic display of construction data, which will significantly benefit the synergistic and reduce the manual work on construction analysis. The data update is mainly about the project participants to update the actual construction data in the graph database for other participants to search and analyze.