4.2.6 metadata

<!ENTITY % MetadataType "THREDDS | ADN | Aggregation | DublinCore |
         % DIF | FGDC | LAS | Other">

<!ELEMENT metadata ANY>
<!ATTLIST metadata
    xlink:type (simple) #FIXED "simple"
    xlink:href CDATA #IMPLIED
    metadataType (%MetadataType;) #REQUIRED
>

A metadata element contains or refers to structured information about datasets, which is used by client programs to properly display or search for the dataset. Typically, metadata is not displayed to an end-user when making selections from the catalog, although it may be useful to make it optionally available. We call this kind of content "machine readable" information.

The metadata element must contain a metadataType attribute whose value comes from a controlled vocabulary. The types and formats of the metadata are still being developed, and the current list should be considered experimental. Most are currently not operational.

THREDDS

a/k/a "Dataset Description"

ADN

Alexandria / DLESE format

Aggregation

DODS/OPeNDAP Aggregation Server

DublinCore

Dublin Core

DIF

NASA's Global Change Master Directory (GCMD) format

FGDC

Federal Geographic Data Committee

LAS

Live Access Server

The metadata content may be placed in the metadata element itself, or it may be pointed to through an XLink, but it may not have both. Generally when the metadata is referenced by an XLink, the information is not read until explicitly requested.