C: Identifier

Definition: An unambiguous reference to the resource within a given context.

Obligation: Conditional - mandatory for online resources, otherwise recommended where available. Not used for services.

What is this element?

An Identifier is a reference that includes enough information to unambiguously trace the original item described.

Identifiers can be useful for finding a specific resource, for confirming that you have the correct version, and as shorthand for references to the resource. Search tools that fully index will allow a search by Identifier. Often, the first part of the Identifier specifies the context by which the remainder of the Identifier is understood. For example, the letters ISBN indicate that the reference is to a published book.

Non-electronic resources can identified using standard schemas such as ISBN and ISSN. Some published items have 'in-house' identifiers. Examples include forms or leaflets produced by the organisation. While these usually have a code allocated (e.g. IR3 for a tax return form) this code is rarely universally unique (IR3 is also a paintball gun....). Identifiers can be made more specific by prefixing them with the Agency code, which is allocated to each government department and agency by Archives New Zealand.

For online resources, the identifier for online resources will usually be a URI, but identification codes automatically allocated by records management systems can be used, if useful for public identification of information. When entering a URI, use copy and paste, if you can. This reduces the risk of typing errors.

URIs should not be used as identifiers where:

• a website has been set up to dynamically generate URIs;
• a resource is held in a 'temporary' location e.g. 'current' news releases and will later be moved to a location with an associated permanent URI;
• one metadata record is being used to describe an online publication that is available in more than one digital format (e.g. available as either a PDF or HTML document).

In these cases give whatever stable URI provides the easiest access path to the resource(s) as Availability.

It is not always possible to find a unique identifier for a resource, especially if for an online resource it is not practical to use the URI.

Identifier and other elements

The Availability element can be used with the Identifier element to show how to obtain the resource.

Repetition

You may repeat the element if appropriate - e.g. some books that are published as part of a series have both an ISBN and an ISSN.

Qualifiers

Encoding Schemes

Recommended best practice is to identify the resource using an appropriate formal identification system such as:

• URI - Uniform Resource Identifier for online or electronic resources. This includes the other schemes "Uniform Resource Locator" (URL) and "Uniform Resource Names" (URN).
  Enter a URI in full, i.e. you must include the part before the colon as it identifies the scheme being used, e.g. http://.
  See: RFC2396: Uniform Resource Identifiers (URI): Generic Syntax, August 1998 http://www.ietf.org/rfc/rfc2396.txt
• ISBN - International Standard Book Number - for books. Include the hyphens as punctuation. See: http://www.isbn-international.org/whatis.html
• ISSN - International Standard Serial Number - for serials. Include the hyphen as punctuation. See: http://www.issn.org:8080/English/pub/faqs/issn
• ISMN - International Standard Music Number - for printed music. See: http://www.ismn-international.org/whatis.html
• Digital Object Identifier (DOI) - for electronic publications, especially in online form. http://www.doi.org/index.html
• Archives New Zealand GAIMS Agency code - contact Archives New Zealand.

Examples