The function of identification is to map a known quantity to an unknown entity so as to make it known. The known quantity is called the identifier (or ID) and the unknown entity is what needs identification. A basic requirement for identification is that the ID be unique. IDs may be scoped, that is, they are unique only within a particular scope. IDs may also be built out of a collection of quantities such that they are unique on the collective. For data storage, identification is the capability to find, retrieve, report, change, or delete specific data without ambiguity. This applies especially to information stored in databases. In database normalisation, the process of organizing the fields and tables of a relational database to minimize redundancy and dependency, is the central, defining function of the discipline.