## 3 Methodology
### Collaborative Management of Micro-Meso Information
#### 3.1.2 Standard Unification  
Every task in the entire lifecycle of a construction project contributes to the improvement and expansion of the BIM database to some extent. With the gradual penetration and application of BIM technology, the classification and coding standards of data information used in different software or regions often differ. Data coding is the key to achieving interconnection and interoperability among engineering objects, such as models, data, components, and entities, and is also critical to tracking changes in data information. Therefore, it is essential for construction units or government units in a certain region to require the use of a unified BIM data standard system in different BIM software to facilitate the transmission and use of data among all parties involved. This is necessary to achieve data collaboration between different levels of units. Between the construction units and the contractor units, the construction units can base their BIM data coding system design on the local standard coding system established by government units, combined with China's \"Building Information Model Classification and Coding Standard\" and the international OmniClass standard. The coding classification of BIM data should follow basic principles, such as scientificity, systematicity, uniqueness, scalability, retrievability, and practicality [29]. Based on the characteristics and attributes of engineering information content, it should be classified according to a certain logic and method, and a certain classification system should be established to ensure that each element or component has a unique identification code and the connection between BIM model elements, components, and data coding system is realized. Basic data coding content is usually encoded using a combination of letters, numbers, symbols, or other methods to ensure the uniqueness and effective transmission of information. The hierarchical structure of the coding system follows a basic paradigm as shown in example in Figure 8. In the coding structure, the classification code should be standardized, while the serial code can be customized according to the specific engineering project. However, it is recommended to use continuous numbering for objects of the same category, starting with \"01\" or \"0001\". Taking a general construction project as an example, the standardized objects for common basic data coding include project civil engineering objects, project construction objects, etc. The general rules of the data coding standard can provide unified requirements for different objects. For example, in the coding character type, \"A\" represents letters, \"N\" represents the Arabic numerals 0-9, \"C\" represents a combination of \"A\" (letter) and \"N\" (number), and \"0\" is used to fill in when the coding digit number is insufficient. * Project civil engineering objects  
Project civil engineering objects refer to the civil engineering BIM data objects in the construction process of a project, including all the components within the civil engineering system. These objects can be composed of a project code, a functional building code, and a civil engineering object code. The data coding structure is shown in Figure 9.  
Figure 8: Data coding hierarchy basic paradigm. * Project construction objects  
Project construction objects refer to the objects related to the BIM data acceptance of construction management during the project planning and construction process, which are divided according to the minimum inspection batch. The data coding of these objects can be composed of a project code, a unit engineering code, a divisional engineering code, an itemized engineering code, and a pipelining code. The coding structure is shown in Figure 10.  
Figure 10: Project construction object data coding structure. Figure 9: Data coding structure of project civil engineering objects. Regarding the quick assignment of codes, different BIM software have their own ways of processing.