NSDI XML metadata schemas

NSDI metadata must be encoded in XML document format. The XML format of the NSDI metadata document is specified by the following XML schemas:

CSW2 AP ISO,
ISO 19139 from the repository of ISO schemes,
ISO 19139 from the repository of OGC schemes.

One of these XML schemas must be used as the basis for documenting NSDI metadata. All three XML metadata schemas declare the same XML metadata document namespace http://www.isotc211.org/2005/gmd (gmd prefix). The choice of XML schema depends on the available technical solutions and the version of GML used:

if the metadata will be shared by a discovery service that supports the CSW2 AP ISO standard, it is recommended to use the XML implementation of that standard, or the CSW2 AP ISO XML schema. This XML schema uses GML version 3.2.1.
if GML version 3.2.1 is used to document metadata (namespace http://www.opengis.net/gml/3.2, gml prefix), it is recommended to use version 20070417 of the ISO 19139 XML schema from the OGC repository.
if GML version 3.2.0 is used to document metadata (namespace http://www.opengis.net/gml, gml prefix), it is recommended to use the ISO 19139 XML schema from the ISO repository or an almost identical version of the 20060504 ISO 19139 XML schema from OGC repository.

As a basis for documenting spatial data service identification information, an XML metadata schema for spatial data services from the OGC schema repository must be used. The OGC XML service metadata schema is an implementation of the ISO 19119 service metadata standard and declares a http://www.isotc211.org/2005/srv XML document namespace (srv prefix).

ISO 19139 XML schemas, unlike CSW2 AP ISO XML schemas, do not directly include a srv namespace, ie an XML schema for documenting service identification information. Therefore, if ISO 19139 XML schemas are used to document metadata, depending on the version of the ISO 19139 XML schema, that is, the GML version, when implementing the service metadata, it is necessary to include the appropriate version of the srv XML schema to document the service identification information. Therefore, if used:

GML version 3.2.1 it is necessary to include version 20070417 of the srv XML schema,
GML version 3.2.0 it is necessary to include version 20060504 of the srv XML schema.