An identifier which form depends on the system under which the identifier was defined.

An indication of the scope of the identifier in subfield a (if present), usually the name of a publisher, an indication of the binding of the item, or an indication of the relationship of an identifier to a set or to a particular volume.

The price of the item and any comment on its availability.

An identifier that has been identified as being erroneously applied to an item or it is otherwise invalid. It may have been allocated to two different publications or products and in this instance cancelled, or it may have been incorrectly printed.

A code indicating system under which the identifier was defined.

The DOI name structure is standardized as ISO 26324:2012.

The DOI name structure is made up of a prefix element and a suffix element separated by a forward slash "/", e.g. 10.1000/12345.

The DOI name prefix (e.g. 10.1000) is composed of two components separated by a full stop. The first part "10" is the directory number and it remains the same for all DOI names. The second part (e.g. 1000) is a unique alphanumeric string assigned to an organization that wishes to register DOI names. The second part of the prefix may be further divided into sub-elements, each of them preceded by a full stop (e.g. 1000.10). There are no limitations concerning the amount of DOI names that the registration agency could ask for. The prefix of the DOI name does not provide evidence of the ownership or rights or current management responsibility of any intellectual property.

The prefix is followed by a forward slash "/" and a unique suffix (e.g., 12345), which indicates the entity. The combination of a prefix element indicating the registrant, and the unique suffix element chosen by the registrant, suppress the need for the centralized management of DOI names.

The suffix element may be a sequential number, or it may incorporate identifier from or based on another system used by the registrant, e.g. ISBN, ISSN, PII, SICI … (see examples 1, 2). The existent identifiers and/or bibliographical data used for the suffix element have no particular meaning within the DOI system.

The ISAN (International Standar Audiovisual Number) is a numbering system which is standardized as ISO 15706:2002 and ISO 15706-2:2007 for V-ISAN.

ISAN may be 17-digit or 26-digit identifier.

A 17-digit ISAN consists of 16 hexadecimal digits (characters: 0 to 9 and A do F), divided into two segments followed by a check digit. The first segment, which consists of 12-digit root segment, is followed by the second segment which consists of 4-digit segment for the identification of episodes or parts when applicable. When a work is not an episode or part of a serial audiovisual work, the segment should consist of zeros. An alphanumerical check digit is also appended to the last segment (characters: 0 to 9 and A to Z).

Except 17-digit ISAN, the 26-digit ISAN (V-ISAN) consists of 8 hexadecimal digits indicating the version; an alphanumerical check digit is also appended to that segment.

Example ISAN 1881-66C7-3420-0000-7-9F3A-0245-U:

The prefix ISAN and the check digit as the 17th character (and as the 26th character when also version identifier is added to ISAN) are always present when ISAN is displayed in human-readable form. Each group of 4 hexadecimal digits and also the check digit is separated by hyphens or spaces.

V-ISAN is a combination of the international standard audiovisual number (ISAN) for the primary work and the added version identifier (see example 3).

The Handle system is defined in the RFC 3650, 3651 and 3652 documents of the Internet Engineering Task Force (IETF) and is intended to resolve URLs with the help of the Handle.Net Registry.

The handle identifier is composed of a prefix and a suffix separated by a forward slash "/", e.g., 20.1000/100.

The prefix designates the naming authority. If the prefix consists of multiple parts, these are separated by periods and represent segments in the hierarchy of the naming authority. Each handle identifier prefix starts with a "20" and represents the CNRI – Corporation for National Research Initiatives, followed by identifiers of organizations registered at the Handle.Net Registry (see examples 4, 5). The prefix can consist of any Unicode UCS-2 characters other than "/".

The prefix is followed by a forward slash and a suffix designating the local name of the resource. The suffix can consist of any Unicode UCS-2 characters.

The letters, which are usually found printed with the identifier on the item, should not be entered in field 017.

Each identifier, which is found to be wrongly printed, can be entered in subfield 017z – Erroneous identifier.

Hyphens or forward slash inserted in subfields a and z separate different parts of an identifier.

In order to distinguish between identifiers, when there is more than one in a record, qualifications may be added to one or more of them.

Terms of availability and price are often related to each identifier. Thus this information is recorded in the same field.

The field should be repeated for each valid identifier. It should also be repeated for an invalid identifier unless that invalid identifier clearly relates to a known valid identifier entered in the record, in which case the invalid identifier will be entered in the same field as its corresponding valid identifier.