to engineer the database system. Disadvantages Usage of natural keys as unique identifiers in a table has one main disadvantage which is the change of business rules or the change of rules of the attribute in the real world. The definition of the structure of the natural key attribute might change in the future. For example if there is a table storing the information about US citizens, the Social Security Number would act as the natural key, Social Security Number being the natural key might pose a problem in the future if the US government changes the structure of the Social Security Number and increases the number of digits in the SSN due to some reason. In that case, the Database Administrator will have to change the schema of the table and perhaps also update the records of the table. In other cases, this can prevent improvements of the system altogether due to too extensive effort required for the change, e.g., the inability of the knowledge management system, Confluence, to represent multiple pages with the same title. References Data modeling