gml:EnvelopeWithTimePeriod is provided for envelopes that include a temporal extent. It adds two time position properties, gml:beginPosition and gml:endPosition, which describe the extent of a time-envelope. Since gml:EnvelopeWithTimePeriod is assigned to the substitution group headed by gml:Envelope, it may be used whenever gml:Envelope is valid.
<element name="EnvelopeWithTimePeriod" type="gml:EnvelopeWithTimePeriodType" substitutionGroup="gml:Envelope"><annotation><documentation>gml:EnvelopeWithTimePeriod is provided for envelopes that include a temporal extent. It adds two time position properties, gml:beginPosition and gml:endPosition, which describe the extent of a time-envelope. Since gml:EnvelopeWithTimePeriod is assigned to the substitution group headed by gml:Envelope, it may be used whenever gml:Envelope is valid.</documentation></annotation></element>