The content model is a straightforward extension of gml:AbstractFeatureType; it automatically has the gml:identifier, gml:description, gml:descriptionReference, gml:name, and gml:boundedBy properties. The gml:validTime element describes the time of the observation. Note that this may be a time instant or a time period.The gml:using property contains or references a description of a sensor, instrument or procedure used for the observation.The gml:target property contains or references the specimen, region or station which is the object of the observation. This property is particularly useful for remote observations, such as photographs, where a generic location property might apply to the location of the camera or the location of the field of view, and thus may be ambiguous. The gml:subject element is provided as a convenient synonym for gml:target. This is the term commonly used in phtotography. The gml:resultOf property indicates the result of the observation. The value may be inline, or a reference to a value elsewhere.
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.
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<element name="Observation" type="gml:ObservationType" substitutionGroup="gml:AbstractFeature"><annotation><documentation>The content model is a straightforward extension of gml:AbstractFeatureType; it automatically has the gml:identifier, gml:description, gml:descriptionReference, gml:name, and gml:boundedBy properties. The gml:validTime element describes the time of the observation. Note that this may be a time instant or a time period. The gml:using property contains or references a description of a sensor, instrument or procedure used for the observation. The gml:target property contains or references the specimen, region or station which is the object of the observation. This property is particularly useful for remote observations, such as photographs, where a generic location property might apply to the location of the camera or the location of the field of view, and thus may be ambiguous. The gml:subject element is provided as a convenient synonym for gml:target. This is the term commonly used in phtotography. The gml:resultOf property indicates the result of the observation. The value may be inline, or a reference to a value elsewhere.</documentation></annotation></element>