Persistent identifiers are identifiers that can be cited to retrieve digital objects over a long period of time. Such identifiers enable resources to be accurately identified by reconciling a publicly visible ID to the current address of the metadata or content in a catalogue or digital store even when this changes over time. As national bibliographies develop new online or linked data services the issue of permanent identifiers for citation and linking is becoming increasingly crucial at the international level.

More information on persistent identifiers can be found in an article by E. Bermès (2006)