Top-level Element: <identifier>
| Element | <identifier> |
|---|---|
| Definition | Contains a unique standard number or code that distinctively identifies a resource. |
| Attributes | type; displayLabel; invalid; altRepGroup; lang; xml:lang; script; transliteration; typeURI |
| Subelements | None |
GUIDELINES | EXAMPLES | MAPPINGS
GUIDELINES FOR USE
<identifier> includes manifestation, expression, and work level identifiers.
MODS makes a distinction between a persistent identifier of the resource and its electronic location. This element is used for the former; <location><url> is used for the latter.
Repeat the <identifier> element for each applicable identifier recorded, including invalid and canceled identifiers.
Specific DLF/Aquifer Guidelines
The DLF/Aquifer Implementation Guidelines for Shareable MODS Records recommend the use of at least one <identifier> element with the type attribute containing appropriate values in each MODS record.
The <identifier> element is recommended in these guidelines and refers to the digital resource being described or to its analog equivalent. In the shared metadata context, the <identifier> should identify the object universally.
The guidelines recommend that <identifier> be used to encode any identifying character string uniquely associated with a resource, but reserves <location><url> for encoding the URL to the resource in its repository context. Persistent URIs that serve both as a unique identifier and a URL to the resource in its repository context should be encoded using both elements.
These guidelines require that all <identifier> URLs follow the URI specifications laid out in the DLF/NSDL Best Practices for Shareable Metadata Content.
All occurrences of the <identifier> element must contain the type attribute to indicate the type of the identifier. If a local identifier is used, it should be indicated as such using the "local" value.
See the <identifier> entry in the DLF/Aquifer Summary of MODS Requirements and Recommendations Table for further information on requirements of this element, its attributes, and subelements.
Aggregator information: <identifier> is displayed in some aggregators but is generally not used for retrieval. It may in the future be used to de-duplicate aggregations.
Identifier is addressed in the "Recommendations for classes of data elements" under "Identifiers." The DLF/Aquifer guidelines recommend the use of the type attribute in lieu of prefixing identifiers, as recommended in DLF/NSDL Best Practices for Shareable Metadata 
.
Element Description
Attributes
type
There is no controlled list of identifier types. Suggested values include, but are not limited to, those specified in Standard Identifier Source Codes.
invalid
- yes – This value is used only when recording a canceled or invalid identifier. If invalid="yes" is not present, the identifier is assumed to be valid. Do not use invalid="no."
altRepGroup; lang; xml:lang; script; transliteration; typeURI; displayLabel
Subelements
There are no subelements for <identifier>.
EXAMPLES
MAPPINGS
MARC Mapping (Bibliographic)
<identifier> ≈ MARC 21 fields 010, 020, 022, 024, 856 (only when string begins urn:hdl, urn:doi, hdl: or doi:)
See also MARC Mapping to MODS for the <identifier> element.
Dublin Core Mapping
The MODS <identifier> element, along with the <location><URL>, are both mapped to <dc:identifier> in the MODS to Dublin Core Metadata Element Set Mapping.
MODS examples expressed in Dublin Core:
<dc:identifier>00694010</dc:identifier>
<dc:identifier>hdl:loc.mbrsmi/animp.4068</dc:identifier>
Last Updated: February 19, 2013