## 3 Comprehensive Analysis of Issues of CIM-Based DMS Using RDB
### Difficulty of Changing Database Schema  
With the rising usage of EVs, charging stations for them are being integrated into the power distribution network. Additionally, new facilities such as converter stations and soft-open points (SOPs) are being introduced with the emergence of DC networks. These new elements impact not only the components but also the operation and system of the distribution network. As the power business progresses, the information model for a DMS undergoes modifications. Conversely, if certain equipment becomes obsolete, the associated information model is deleted. If the same element has a different usage concept or is expanded, changes to the information model become imperative. Figure 6 illustrates changes in the information model, reflecting additions of new equipment, removal of existing ones, and modifications of existing components, due to the transformation of the power distribution network operating system. Upon implementing the SOP for operating  
Figure 5: An example of the RDB schema design for objects: (**a**) class tabulation; (**b**) object tabulation. the DC power distribution network, the new SoftOpenPoint class can be introduced to the existing information model. In scenarios where SOP replaces the existing switch equipment, the Switch class might be removed. Given that the existing information model addresses AC networks, adjustments can be made to accommodate DC networks by converting the ACLineSegment class to the LineSegment class. An information model can be extended or modified to accommodate new data requirements arising from new demands or business needs. Due to the characteristics of the information model, the CIM-based DMS can adapt to changes in the power business. However, aligning the schema in the RDB with the updated information model in the DMS necessitates modification. However, RDBs are not structured to easily accommodate changes in the data model. They come with constraints aimed at maintaining data consistency, and altering the schema changes entails additional effort to ensure data integrity. Complex tasks, including modifying table structures and constraints, rebuilding indexes, and adjusting correlations between tables, are necessary. These tasks impact multiple components connected to the database, leading to confusion and increased costs for schema modifications. The scenario where a database schema is altered due to modifications in the information model can be classified as shown in Figure 7. Changes in CIM components are classified into modifying, deleting, and adding. Modifications to CIM elements are classified as changes in class names, attribute names, and correlations. Correlations can transit between association and aggregation, and vice versa. The generalization relationship may also change, or aggregation or association may transit to generalization. Deletion of CIM elements falls into three categories: class deletion, attribute deletion, and correlation deletion. The addition of CIM elements can be classified into cases where the top-level class, sub-class, or attribute name is added, as well as when aggregation, association, or generalization is added. Types of correlations include aggregation, association, and generalization. Figure 6: Change in the information model due to new requirements on the power industry business: (**a**) deletion; (**b**) addition and update. Various scenarios for database schema changes are shown in Table 3. If there are modifications, deletions, or additions to the new CIM elements, the database schema must undergo alterations and migration. Migration involves transferring data from an existing database to a new one in accordance with its structure. Analyzing changes in the information model is necessary to redesign certain components based on the existing RDB schema, considering the modifications. A database migration file can be generated to modify the RDB schema according to the redesigned schema.