Librarianship is the profession of working with information or data as a profession. Often known as "library science" and widely considered to be a subfield of information science, it has roots going back to at least the time of Ancient Egypt. A professional librarian is expected to understand both the theoretical foundations of libraries and information science organization as a whole, but also have an understanding of the practical aspects relating to the up keep of actual libraries, including management duties and even physical work such as shelving books.