diff --git a/SI_Format.xsd b/SI_Format.xsd
index 2672705cd28b62754bb6c5d38063075af90125d7..8557e0fe9e401017ab8f46b5cc53fd7b8391bafc 100644
--- a/SI_Format.xsd
+++ b/SI_Format.xsd
@@ -621,8 +621,8 @@
 							multivariate measurement uncertainty
 						</xs:documentation>
 					</xs:annotation>
-					<xs:element name="ellipsoidalRegionXMLList" type="si:ellipsoidalRegionType"/>
-					<xs:element name="rectangularRegionXMLList" type="si:rectangularRegionType"/>
+					<xs:element name="ellipsoidalRegionXMLList" type="si:ellipsoidalRegionXMLListType"/>
+					<xs:element name="rectangularRegionXMLList" type="si:rectangularRegionXMLListType"/>
 				</xs:choice>
 			</xs:sequence>
 		</xs:complexType>
@@ -793,6 +793,33 @@
 			</xs:sequence>
 		</xs:complexType>
 
+		<xs:complexType name="covarianceMatrixXMLListType">
+			<xs:sequence>
+				<xs:element name="column" minOccurs="1" maxOccurs="unbounded">
+					<xs:annotation>
+						<xs:documentation xml:lang="en">
+							Definition of a column in the covariance matrix.
+						</xs:documentation>
+						<xs:documentation xml:lang="en">
+
+						</xs:documentation>
+					</xs:annotation>
+					<xs:complexType>
+						<xs:sequence>
+								<xs:annotation>
+									<xs:documentation xml:lang="en">
+
+									</xs:documentation>
+								</xs:annotation>
+								<xs:sequence>
+									<xs:element name="covarianceValueXMLList" type="si:decimalXMLListType"/>
+									<xs:element name="covarianceUnitXMLList" type="si:unitXMLListType"/>
+								</xs:sequence>
+						</xs:sequence>
+					</xs:complexType> 
+				</xs:element>
+			</xs:sequence>
+		</xs:complexType>
 	
 		<xs:complexType name="ellipsoidalRegionType">
 			<xs:sequence>
@@ -805,6 +832,19 @@
 				<xs:element name="distribution" type="xs:string" minOccurs="0"/>
 			</xs:sequence>
 		</xs:complexType>
+	
+	
+		<xs:complexType name="ellipsoidalRegionXMLListType">
+			<xs:sequence>
+				<!-- covariance matrix data -->
+				<xs:element name="covarianceMatrixXMLList" type="si:covarianceMatrixXMLListType"/>
+				<!-- coverage properties of region -->
+				<xs:element name="coverageFactorXMLList" type="si:kValueXMLListType"/>
+				<xs:element name="coverageProbabilityXMLList" type="si:probabilityValueXMLListType"/>
+				<!-- optional information about distribution -->
+				<xs:element name="distributionXMLList" type="si:stringXMLListType" minOccurs="0"/>
+			</xs:sequence>
+		</xs:complexType>
 		
 		
 		<xs:complexType name="rectangularRegionType">
@@ -818,6 +858,18 @@
 				<xs:element name="distribution" type="xs:string" minOccurs="0"/>
 			</xs:sequence>
 		</xs:complexType>
+	
+		<xs:complexType name="rectangularRegionXMLListType">
+			<xs:sequence>
+				<!-- covariance matrix data -->
+				<xs:element name="covarianceMatrixXMLList" type="si:covarianceMatrixXMLListType"/>
+				<!-- coverage properties of region -->
+				<xs:element name="coverageFactorXMLList" type="si:kValueXMLListType"/>
+				<xs:element name="coverageProbabilityXMLList" type="si:probabilityValueXMLListType"/>
+				<!-- optional information about distribution -->
+				<xs:element name="distributionXMLList" type="si:stringXMLListType" minOccurs="0"/>
+			</xs:sequence>
+		</xs:complexType>
 		
 		
 		<xs:complexType name="listUnivariateUncType">