dc:Identifier
The publication date, expressed as YYYY-MM-DD: a mandatory 4-digit year, followed by an optional 2-digit month and an optional 2-digit day of the month.

attributes

id
Provides an element with a unique name within a single document. This is especially useful in works with extensive cross-referencing and linking, such as dictionaries, encyclopedias, or travel guides. Use of ids simplifies linking and updates.
xml:lang
xml language code.
xmlns:dc
Always equal to "http://purl.org/dc/elements/1.0/"
scheme
identifier scheme

Sample:

<dc:Identifier id="isbn">0-123-45678-9</dc:Identifier>

See also:

<dc-metadata>