<?xml version="1.0" encoding="UTF-8"?>
<schema targetNamespace="http://www.opengis.net/gml" xmlns="http://www.w3.org/2001/XMLSchema" xmlns:gml="http://www.opengis.net/gml" elementFormDefault="qualified" version="3.1.1">
	<annotation>
		<appinfo source="urn:opengis:specification:gml:schema-xsd:observation:3.1.1">observation.xsd</appinfo>
		<documentation>Observation schema for GML 3.1     
    Copyright (c) 2002-2005 OGC, All Rights Reserved.
	For conditions, see OGC Software Notice http://www.opengeospatial.org/about/?page=ipr</documentation>
	</annotation>
	<!-- =================================================================== -->
	<!-- ===       includes and imports ============================================ -->
	<include schemaLocation="feature.xsd"/>
	<include schemaLocation="direction.xsd"/>
	<include schemaLocation="valueObjects.xsd"/>
	<!-- =================================================================== -->
	<!-- =================== properties =================================== -->
	<element name="using" type="gml:FeaturePropertyType">
		<annotation>
			<documentation>This element contains or points to a description of a sensor, instrument or procedure used for the observation</documentation>
		</annotation>
	</element>
	<!-- =================================================================== -->
	<element name="target" type="gml:TargetPropertyType">
		<annotation>
			<documentation>This element contains or points to the specimen, region or station which is the object of the observation</documentation>
		</annotation>
	</element>
	<!-- =================================================================== -->
	<element name="subject" type="gml:TargetPropertyType" substitutionGroup="gml:target">
		<annotation>
			<documentation>Synonym for target - common word used for photographs</documentation>
		</annotation>
	</element>
	<!-- =================================================================== -->
	<complexType name="TargetPropertyType">
		<annotation>
			<documentation>Container for an object representing the target or subject of an observation.</documentation>
		</annotation>
		<sequence minOccurs="0">
			<choice>
				<element ref="gml:_Feature"/>
				<element ref="gml:_Geometry"/>
			</choice>
		</sequence>
		<attributeGroup ref="gml:AssociationAttributeGroup"/>
	</complexType>
	<!-- =================================================================== -->
	<element name="resultOf" type="gml:AssociationType">
		<annotation>
			<documentation>The result of the observation: an image, external object, etc</documentation>
		</annotation>
	</element>
	<!-- =================================================================== -->
	<!-- ===================== Features =========================== -->
	<element name="Observation" type="gml:ObservationType" substitutionGroup="gml:_Feature"/>
	<!-- =========================================================== -->
	<complexType name="ObservationType">
		<complexContent>
			<extension base="gml:AbstractFeatureType">
				<sequence>
					<element ref="gml:validTime"/>
					<element ref="gml:using" minOccurs="0"/>
					<element ref="gml:target" minOccurs="0"/>
					<element ref="gml:resultOf"/>
				</sequence>
			</extension>
		</complexContent>
	</complexType>
	<!-- =========================================================== -->
	<element name="DirectedObservation" type="gml:DirectedObservationType" substitutionGroup="gml:Observation"/>
	<!-- =========================================================== -->
	<complexType name="DirectedObservationType">
		<complexContent>
			<extension base="gml:ObservationType">
				<sequence>
					<element ref="gml:direction"/>
				</sequence>
			</extension>
		</complexContent>
	</complexType>
	<!-- =========================================================== -->
	<element name="DirectedObservationAtDistance" type="gml:DirectedObservationAtDistanceType" substitutionGroup="gml:DirectedObservation"/>
	<!-- =========================================================== -->
	<complexType name="DirectedObservationAtDistanceType">
		<complexContent>
			<extension base="gml:DirectedObservationType">
				<sequence>
					<element name="distance" type="gml:MeasureType"/>
				</sequence>
			</extension>
		</complexContent>
	</complexType>
	<!-- =========================================================== -->
</schema>