4.4 Identifier Characteristics

4.4.1     The following characteristics should be considered when developing a naming scheme:     Uniqueness, the naming scheme must be unique within the context of the organisation’s digital resources and, if necessary, globally unique.     There should be a commitment to persistence; an organisation must have a commitment to maintain the association of the current location of the resource with the persistent identifier.     An identifier system will be more effective if it is able to accommodate the special requirements of different types of material or collections.     Although not absolutely critical, and not essential for machine generated persistent identifiers, a system will generally be more successful if it is easy to understand and apply, and if it lends itself to short and easy to use citations.     The identifier should be capable of distinguishing parts of an item, as well as versions and roles that a digital item might have. Relying on the file extension to distinguish a distribution copy from an archival copy is not advisable as the format may change over time, though the role remains the same (Dack 1999).     The identifier should permit batch renaming for ingestion into different content management systems.