diff --git a/Examples/01 - VerySimpleFixedPVC2_without_electrical_layout.pvc2 b/Examples/01 - VerySimpleFixedPVC2_without_electrical_layout.pvc2
index b577f49..42e7e04 100644
--- a/Examples/01 - VerySimpleFixedPVC2_without_electrical_layout.pvc2	
+++ b/Examples/01 - VerySimpleFixedPVC2_without_electrical_layout.pvc2	
@@ -196,7 +196,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_terrain tag, might not have any child tags at the start but can be useful in the future -->
-							<pv:instance_terrain />
+							<pv:instance_terrain id="InstanceTerrain" />
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -207,7 +207,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable1">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId1" url="#rackInstance1" />
 								</pv:instance_racks_array>
@@ -223,7 +223,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable2">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId2" url="#rackInstance1" />
 								</pv:instance_racks_array>
@@ -239,7 +239,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable3">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId3" url="#rackInstance1" />
 								</pv:instance_racks_array>
diff --git a/Examples/02 - TrackersPVC2_without_electrical_layout.pvc2 b/Examples/02 - TrackersPVC2_without_electrical_layout.pvc2
index 26698fa..8ba1857 100644
--- a/Examples/02 - TrackersPVC2_without_electrical_layout.pvc2	
+++ b/Examples/02 - TrackersPVC2_without_electrical_layout.pvc2	
@@ -577,7 +577,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_terrain tag, might not have any child tags at the start but can be useful in the future -->
-							<pv:instance_terrain />
+							<pv:instance_terrain id="InstanceTerrain" />
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -587,7 +587,7 @@
 				<instance_node url="#TrackerModel1">
 					<extra>
 						<technique profile="PVCollada-2.0">
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable1">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId1-1" url="#rackInstance1"/>
 									<pv:instance_rack_ref id="rackId1-2" url="#rackInstance2"/>
@@ -605,7 +605,7 @@
 				<instance_node url="#TrackerModel1">
 					<extra>
 						<technique profile="PVCollada-2.0">
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable2">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId2-1" url="#rackInstance1"/>
 									<pv:instance_rack_ref id="rackId2-2" url="#rackInstance2"/>
@@ -623,7 +623,7 @@
 				<instance_node url="#TrackerModel1">
 					<extra>
 						<technique profile="PVCollada-2.0">
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable3">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId3-1" url="#rackInstance1"/>
 									<pv:instance_rack_ref id="rackId3-2" url="#rackInstance2"/>
diff --git a/Examples/03 - VerySimpleFixedPVC2_with_basic_electrical_layout.pvc2 b/Examples/03 - VerySimpleFixedPVC2_with_basic_electrical_layout.pvc2
index 704a62b..d567a9c 100644
--- a/Examples/03 - VerySimpleFixedPVC2_with_basic_electrical_layout.pvc2	
+++ b/Examples/03 - VerySimpleFixedPVC2_with_basic_electrical_layout.pvc2	
@@ -326,7 +326,7 @@
 						<technique profile="PVCollada-2.0">
 							<!-- instance_terrain tag, might not have any child tags at the start
 							but can be useful in the future -->
-							<pv:instance_terrain></pv:instance_terrain>
+							<pv:instance_terrain id="InstanceTerrain"></pv:instance_terrain>
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -337,7 +337,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable1">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId1" url="#rackInstance1" />
 								</pv:instance_racks_array>
@@ -353,7 +353,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable2">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId2" url="#rackInstance1" />
 								</pv:instance_racks_array>
@@ -369,7 +369,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable3">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId3" url="#rackInstance1" />
 								</pv:instance_racks_array>
diff --git a/Examples/04 - TrackersPVC2_with_basic_electrical_layout.pvc2 b/Examples/04 - TrackersPVC2_with_basic_electrical_layout.pvc2
index e9bee74..529a62d 100644
--- a/Examples/04 - TrackersPVC2_with_basic_electrical_layout.pvc2	
+++ b/Examples/04 - TrackersPVC2_with_basic_electrical_layout.pvc2	
@@ -1395,7 +1395,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_terrain tag, might not have any child tags at the start but can be useful in the future -->
-							<pv:instance_terrain/>
+							<pv:instance_terrain id="InstanceTerrain"/>
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -1405,7 +1405,7 @@
 				<instance_node url="#TrackerModel1">
 					<extra>
 						<technique profile="PVCollada-2.0">
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable1">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId1-1" url="#rackInstance1"/>
 									<pv:instance_rack_ref id="rackId1-2" url="#rackInstance2"/>
@@ -1423,7 +1423,7 @@
 				<instance_node url="#TrackerModel1">
 					<extra>
 						<technique profile="PVCollada-2.0">
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable2">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId2-1" url="#rackInstance1"/>
 									<pv:instance_rack_ref id="rackId2-2" url="#rackInstance2"/>
@@ -1441,7 +1441,7 @@
 				<instance_node url="#TrackerModel1">
 					<extra>
 						<technique profile="PVCollada-2.0">
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable3">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId3-1" url="#rackInstance1"/>
 									<pv:instance_rack_ref id="rackId3-2" url="#rackInstance2"/>
diff --git a/Examples/05 - VerySimpleFixedPVC2_with_electrical_layout.pvc2 b/Examples/05 - VerySimpleFixedPVC2_with_electrical_layout.pvc2
index 2d98cd3..04b146f 100644
--- a/Examples/05 - VerySimpleFixedPVC2_with_electrical_layout.pvc2	
+++ b/Examples/05 - VerySimpleFixedPVC2_with_electrical_layout.pvc2	
@@ -552,7 +552,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_terrain tag, might not have any child tags at the start but can be useful in the future -->
-							<pv:instance_terrain />
+							<pv:instance_terrain id="InstanceTerrain" />
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -563,7 +563,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable1">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId1" url="#rackInstance1" />
 								</pv:instance_racks_array>
@@ -579,7 +579,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_inverter3d tag, references the corresponding instance_inverter of the circuit -->
-							<pv:instance_inverter3d instance_inverter_id="inverterInstance1" />
+							<pv:instance_inverter3d id="instanceInverter3D1" instance_inverter_id="inverterInstance1" />
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -591,7 +591,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable2">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId2" url="#rackInstance1" />
 								</pv:instance_racks_array>
@@ -607,7 +607,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_inverter3d tag, references the corresponding instance_inverter of the circuit -->
-							<pv:instance_inverter3d instance_inverter_id="inverterInstance2" />
+							<pv:instance_inverter3d id="instanceInverter3D2" instance_inverter_id="inverterInstance2" />
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -619,7 +619,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_table tag -->
-							<pv:instance_table>
+							<pv:instance_table id="InstanceTable3">
 								<pv:instance_racks_array>
 									<pv:instance_rack_ref id="rackId3" url="#rackInstance1" />
 								</pv:instance_racks_array>
@@ -635,7 +635,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_inverter3d tag, references the corresponding instance_inverter of the circuit -->
-							<pv:instance_inverter3d instance_inverter_id="inverterInstance3" />
+							<pv:instance_inverter3d id="instanceInverter3D3" instance_inverter_id="inverterInstance3" />
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -647,7 +647,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_combiner_ac3d tag, references the corresponding instance_combiner_ac of the circuit -->
-							<pv:instance_combiner_ac3d instance_combiner_ac_id="combinerAcInstance" />
+							<pv:instance_combiner_ac3d id="instanceCombinerAc3D" instance_combiner_ac_id="combinerAcInstance" />
 						</technique>
 					</extra>
 				</instance_geometry>
@@ -659,7 +659,7 @@
 					<extra>
 						<technique profile="PVCollada-2.0">
 							<!-- instance_transformer3d tag, references the corresponding instance_transformer of the circuit -->
-							<pv:instance_transformer3d instance_transformer_id="transformerInstance" />
+							<pv:instance_transformer3d id="instanceTransformer3D" instance_transformer_id="transformerInstance" />
 						</technique>
 					</extra>
 				</instance_geometry>
diff --git a/schema/pvcollada_schema_2.0.xsd b/schema/pvcollada_schema_2.0.xsd
index ebb7ff9..3b3bd77 100644
--- a/schema/pvcollada_schema_2.0.xsd
+++ b/schema/pvcollada_schema_2.0.xsd
@@ -1043,8 +1043,11 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
       terrain (has a terrain tag in its extra/technique tag).</xs:documentation>
     </xs:annotation>
     <xs:complexType>
-      <!-- no child elements allowed -->
-      <xs:sequence />
+      <xs:attribute name="id" use="required" type="xs:ID">
+        <xs:annotation>
+          <xs:documentation>Unique id for the terrain instance</xs:documentation>
+        </xs:annotation>
+      </xs:attribute>  
     </xs:complexType>
   </xs:element>
   <xs:element name="instance_rack">
@@ -1054,7 +1057,7 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
       a model for a rack (has a rack tag in its extra/technique tag).</xs:documentation>
     </xs:annotation>
     <xs:complexType>
-      <xs:attribute name="id" type="xs:ID">
+      <xs:attribute name="id" use="required" type="xs:ID">
         <xs:annotation>
           <xs:documentation>Unique id for the rack instance</xs:documentation>
         </xs:annotation>
@@ -1078,7 +1081,7 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
             <xs:sequence>
               <xs:element name="instance_rack_ref" maxOccurs="unbounded">
                 <xs:complexType>
-                  <xs:attribute name="id" type="xs:ID">
+                  <xs:attribute name="id" use="required" type="xs:ID">
                     <xs:annotation>
                       <xs:documentation>Unique id for the rack instance reference (will be referenced within the strings in the
                       circuit part)</xs:documentation>
@@ -1096,6 +1099,11 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
           </xs:complexType>
         </xs:element>
       </xs:sequence>
+      <xs:attribute name="id" use="required" type="xs:ID">
+        <xs:annotation>
+          <xs:documentation>Unique id for the table instance</xs:documentation>
+        </xs:annotation>
+      </xs:attribute>
     </xs:complexType>
   </xs:element>
   <xs:element name="instance_post">
@@ -1112,7 +1120,7 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
           </xs:annotation>
 	  		</xs:element>
 			</xs:sequence>
-      <xs:attribute name="id" type="xs:ID">
+      <xs:attribute name="id" use="required" type="xs:ID">
         <xs:annotation>
           <xs:documentation>Unique id for the post instance</xs:documentation>
         </xs:annotation>
@@ -1126,7 +1134,7 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
       a model for a gap (has a gap tag in its extra/technique tag).</xs:documentation>
     </xs:annotation>
     <xs:complexType>
-      <xs:attribute name="id" type="xs:ID">
+      <xs:attribute name="id" use="required" type="xs:ID">
         <xs:annotation>
           <xs:documentation>Unique id for the gap instance</xs:documentation>
         </xs:annotation>
@@ -1154,6 +1162,11 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
       a inverter3d (has an inverter3d tag in its extra/technique tag).</xs:documentation>
     </xs:annotation>
     <xs:complexType>
+      <xs:attribute name="id" use="required" type="xs:ID">
+        <xs:annotation>
+          <xs:documentation>Unique id for the inverter3d instance</xs:documentation>
+        </xs:annotation>
+      </xs:attribute>
       <xs:attribute name="instance_inverter_id" type="xs:IDREF">
         <xs:annotation>
           <xs:documentation>Id of the instance_inverter defined in the circuit part</xs:documentation>
@@ -1181,6 +1194,11 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
 	  for a combiner_ac3d (has an combiner_ac3d tag in its extra/technique tag).</xs:documentation>
     </xs:annotation>
     <xs:complexType>
+      <xs:attribute name="id" use="required" type="xs:ID">
+        <xs:annotation>
+          <xs:documentation>Unique id for the combiner_ac3d instance</xs:documentation>
+        </xs:annotation>
+      </xs:attribute>
       <xs:attribute name="instance_combiner_ac_id" type="xs:IDREF">
         <xs:annotation>
           <xs:documentation>Id of the instance_combiner_ac defined in the circuit part</xs:documentation>
@@ -1208,6 +1226,11 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
 	  for a combiner_dc3d (has an combiner_dc3d tag in its extra/technique tag).</xs:documentation>
     </xs:annotation>
     <xs:complexType>
+      <xs:attribute name="id" use="required" type="xs:ID">
+        <xs:annotation>
+          <xs:documentation>Unique id for the combiner_dc3d instance</xs:documentation>
+        </xs:annotation>
+      </xs:attribute>
       <xs:attribute name="instance_combiner_dc_id" type="xs:IDREF">
         <xs:annotation>
           <xs:documentation>Id of the instance_combiner_dc defined in the circuit part</xs:documentation>
@@ -1235,6 +1258,11 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
       for a transformer3d (has an transformer3d tag in its extra/technique tag).</xs:documentation>
     </xs:annotation>
     <xs:complexType>
+      <xs:attribute name="id" use="required" type="xs:ID">
+        <xs:annotation>
+          <xs:documentation>Unique id for the transformer3d instance</xs:documentation>
+        </xs:annotation>
+      </xs:attribute>
       <xs:attribute name="instance_transformer_id" type="xs:IDREF">
         <xs:annotation>
           <xs:documentation>Id of the instance_transformer defined in the circuit part</xs:documentation>
@@ -1262,7 +1290,12 @@ xmlns:collada="http://www.collada.org/2008/03/COLLADASchema">
       for a cable3d (has an cable3d tag in its extra/technique tag).</xs:documentation>
     </xs:annotation>
     <xs:complexType>
-      <xs:attribute name="cable_to_parent_id" type="xs:IDREF">
+      <xs:attribute name="id" use="required" type="xs:ID">
+        <xs:annotation>
+          <xs:documentation>Unique id for the cable3d instance</xs:documentation>
+        </xs:annotation>
+      </xs:attribute>      
+	  <xs:attribute name="cable_to_parent_id" type="xs:IDREF">
         <xs:annotation>
           <xs:documentation>Id of the cable_to_parent defined in the circuit part</xs:documentation>
         </xs:annotation>