Consider this description of a software system that you are developing to keep track of employees and students at a university.
A university wants an application to manage ID cards for people who work for or who attend the university. When a person is hired, they are assigned a unique identifier that we'll call a utor ID. A person may have an arbitrary number of names — first and last, maybe a middle name, maybe just first, maybe seven names. People should be able to change any of their names.
Some people at the university are students. Students also have another unique identifier called a student ID.
When a person's information is displayed, the university wants the full name plus any identifiers, all on one line.