## 2 Data Schema
### Common Data Environment and Metadata Management  
To manage the collaborative production of bridge information, a CDE needs to be implemented, using which engineers can easily access allowed information to undertake their functions. Currently, with the advancements in the information technology industry, the CDE can be implemented in several ways through a variety of solutions and tools. Most importantly, detailed concepts and principles regarding the CDE solution and workflow must be clearly defined in accordance with a unique standard or certain guidelines. The CDE workflow concept is a closed loop involving the creation and exchange of information. First, all \"work in progress\" information is created and developed by the originator or task team; this information is not visible to or accessible by anyone else. The originator reviews and checks this information until it is approved for sharing with other appropriate task teams and delivery teams or with the appointing party. After the peer-reviewing and authorizing procedures, the information is published and authorized for use in further tasks  
Figure 2: Suspension bridge inventory and ID systems. such as detailed design, construction, or asset management. To manage the metadata through a CDE solution, each piece of information is assigned a status, revision, responsible person, submittal date, classification, and description. Through this process of metadata management, the quality assurance check can be undertaken. Each task team has to check every related information container whether it is in accordance with all the requirements or standards on methods and procedures of the project's information production; otherwise, the task team has to reject those unassured information containers and feedback to the originator for correction requirements. Because a project is a process of collaborative work among many organizations, a compliant implementation plan in terms of information creation can enable the development of a federated information model. Hence, any issues or clashes in the information model should be identified during the production of information rather than after the delivery of information. In terms of the object-based principle of information modeling, each structural member consists of two characteristics: \"attribute information\" and \"archive metadata\". The \"attribute information\" characteristic, which includes some non-numerical information, is used to define the member ID, as explained in the previous section. It is a type of \"active\" information in the CDE and includes details on all general physical properties, such as the structure type, geometric shape, nominal size, material property, orientation information (including the position and restriction), and roles of the element in the entire structure system. In addition, the estimation of quantity/cost is necessary. This active information piece is frequently used during the production and delivery of information and during project implementation by all the organizations involved in the project. In contrast, the \"archive metadata\" characteristic in the CDE is a type of \"inactive\" information; this implies that only specific joined organizations or people are assigned to manage and undertake it. Only the most related organizations or engineers are granted access to this information. From the production of information and during the bridge lifecycle, the metadata archive is continuously obtained and linked to the information system through the individual IDs of each structural member, including the shop-drawing documents, inspection and maintenance records, and classification and description for all the related information of each structural member. This need for metadata necessitates the creation of a procedure using which metadata can be transferred among the CDE solutions in case multiple CDE solutions are used among the organizations. These CDE solutions must collaborate efficiently while the information is being developed and exchanged as a part of the CDE workflow.