Unambiguous identification of entities (e.g. persons, corporate bodies, works etc.) will be essential precursors to machine to machine operations and more identifiers are being developed.
Identifiers, such as ISBN and ISSN, are concerned with products (manifestations in FRBR terms). The new generation of identifiers deals with works and expressions and therefore can facilitate the identification of relationships between manifestations and people or institutions.
As the number of identifiers and their associated metadata sets increases, the need to ensure interoperability has been recognised. Because of this ISO TC 46/SC9, Information and documentation, has established an Identifiers Interoperability Group to examine the relationships between commonly used international identifiers including the ISRC (International Standard Recording Code), the ISAN (International Audio Visual Number) and the ISTC (International Standard Text Code).