Other identifiers

Digital Object Identifier

Managed by the International DOI Foundation, the DOI provides a system to support persistent identification of content objects and related entities in digital networks. The DOI is an International Standard (ISO 26324).


ISBN-A is a service that allows an ISBN to be expressed in the DOI system by including it in the syntax string of a DOI. This enables that ISBN to become actionable or clickable on the web. The ISBN-A always identifies the same product as the corresponding ISBN. ISBN-As do not exist automatically for each ISBN since they must be requested and registered in the DOI system. ISBN-A are available from national ISBN Agencies that are also DOI Registration Agencies.

The Italy ISBN Agency also offers an ISBN-A service.

International Standard Music Number

The International Standard Music Number (ISO 10957) identifies publications consisting of musical notation whether for sale, hire or gratis. The registration authority for the ISMN is the International ISMN Agency.

International Standard Name Identifier

Published in March 2012 as a new International Standard, the International Standard Name Identifier will enable the public identities of parties involved in media content industries to be uniquely identified so that they can be clearly disambiguated where otherwise there might be doubt. The parties to be identified may be involved in any stage of activity from creation, to production, management and content distribution chains and can be a natural or legal person, fictional character or groups of such parties. 

International Standard Serial Number

The International Standard Serial Number (ISO 3297) identifies serial publications and other continuing resources, whether available in print or digital formats. The registration authority for the ISSN is the ISSN International Centre.

International Standard Text Code - withdrawn

The International Standard Text Code (ISTC) was published as an International Standard (ISO 21047) in February 2009 and is a numbering system supporting the unique identification of textual works. The different manifestations of a work (e.g. a paperback book, filmscript, e-book) can be associated with the original textual work through the ISTC. 

ISO 21047 was withdrawn as a standard in August 2021.

International Standard Link Identifier

The International Standard Link Identifier (ISLI) was published as an International Standard (ISO 17316) in 2015 and identifies the links between different entities. A "source" entity can be linked to a "target" entity via the ISLI. ISLI can be applied to many different types of entity - from material objects to digital resources to parties (e.g. natural or legal persons) or even abstract items (e.g. time, places). The ISLI does not change the content, access rights or ownership and can be used in conjunction with existing identifiers.  

The registration authority for the ISLI is operated by International Information Content Industry Association (ICIA)

Click here to read ICIA's article about ISLI and ISLI applications related to books.