The base type for coverages is gml:AbstractCoverageType. The basic elements of a coverage can be seen in this content model: the coverage contains gml:domainSet and gml:rangeSet properties. The gml:domainSet property describes the domain of the coverage and the gml:rangeSet property describes the range of the coverage.
The attribute gml:id supports provision of a handle for the XML element representing a GML Object. Its use is mandatory for all GML objects. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs.
Source
<complexType name="AbstractCoverageType" abstract="true"><annotation><documentation>The base type for coverages is gml:AbstractCoverageType. The basic elements of a coverage can be seen in this content model: the coverage contains gml:domainSet and gml:rangeSet properties. The gml:domainSet property describes the domain of the coverage and the gml:rangeSet property describes the range of the coverage.</documentation></annotation><complexContent><extension base="gml:AbstractFeatureType"><sequence><element ref="gml:domainSet"/><element ref="gml:rangeSet"/></sequence></extension></complexContent></complexType>