Object Identiiers, Keys, and Surrogates | Object Identiiers Revisited

Sound naming schemes for objects are crucial in many parts of computer science, such as database model-ing, database implementation, distributed and federated databases, and networked and distributed operating systems. Over the past 20 years, physical pointers, keys, surrogates and object identiiers have been used as naming schemes in database systems and elsewhere. However, there are some persistent confusions about the nature, applicability and limits of these schemes. In this paper we give a detailed comparison of three naming schemes, viz. object identiiers, internal identiiers (often called surro-gates) and keys. We discuss several ways in which identi-cation schemes can be implemented, and show what the theoretical and practical limits of applicability of iden-tiication schemes are, independently from how they are implemented. In particular, we discuss problems with the recognition and authentication of identiiers. If the iden-tiied objects are persons, an additional problem is that object identiication may connict with privacy demands; for this case, we indicate a way in which identiication can be combined with privacy protection.