diff --git a/SI_Format.xsd b/SI_Format.xsd
index 2f178c9a1f11d91eb311778b9ae5d609eff3376a..8a1e0a247c3ab3a3988a4fe6aad4b36853f566d9 100644
--- a/SI_Format.xsd
+++ b/SI_Format.xsd
@@ -480,12 +480,325 @@
 				 
 				(m) - id								(unique identifier)
 				(o) - label								(string)
-				
+				(m) - distribution						(sub structure distribution)
+				(m) - unit								(string - SI unit)
 				]]>
 			</xs:documentation>
 		</xs:annotation>
 	</xs:element>
 	
+	<xs:element name="distribution" type="si:distributionType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				distribution, which are used by METAS UncLib. This element must always 
+				be used in the context of a distribution, which is an application within 
+				si:uncInput.
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distStandardNormal" type="si:distStandardNormalType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				standard normal distribution (mu = 0, sigma = 1), which are used by METAS UncLib. 
+				This element must always be used in the context of a distribution, which is an 
+				application within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= mu
+				stdunc	= sigma 
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distNormal" type="si:distNormalType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				normal distribution, which are used by METAS UncLib. This element must always 
+				be used in the context of a distribution, which is an application within 
+				si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - mu								(mean)
+				(m) - sigma								(standard deviation)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= mu
+				stdunc	= sigma 
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distStandardUniform" type="si:distStandardUniformType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				standard uniform distribution (a = 0, b = 1), which are used by METAS UncLib.
+				This element must always be used in the context of a distribution, which is an
+				application within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= (a + b) / 2
+				stdunc	= (b - a) / sqrt(12) 
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distUniform" type="si:distUniformType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				uniform distribution, which are used by METAS UncLib. This element must always 
+				be used in the context of a distribution, which is an application within 
+				si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - a									(a)
+				(m) - b									(b)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= (a + b) / 2
+				stdunc	= (b - a) / sqrt(12) 
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distCurvilinearTrapezoid" type="si:distCurvilinearTrapezoidType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating
+				curvilinear trapezoid distribution, which are used by METAS UncLib. This 
+				element must always be used in the context of a distribution, which is an
+				application within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - a									(a)
+				(m) - b									(b)
+				(m) - d									(d)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= (a + b) / 2
+				stdunc	= sqrt((b - a)^2 / 12 + d^2 / 9) 
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distTrapezoidal" type="si:distTrapezoidalType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating
+				trapezoidal distribution, which are used by METAS UncLib. This element must
+				always be used in the context of a distribution, which is an application
+				within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - a									(a)
+				(m) - b									(b)
+				(m) - beta								(beta)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= (a + b) / 2
+				stdunc	= (b - a) * sqrt((1 + beta^2) / 24)
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distTriangular" type="si:distTriangularType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				triangular distribution, which are used by METAS UncLib. This element must
+				always be used in the context of a distribution, which is an application
+				within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - a									(a)
+				(m) - b									(b)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= (a + b) / 2
+				stdunc	= (b - a) / sqrt(24)
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distArcSine" type="si:distArcSineType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				arc sin distribution, which are used by METAS UncLib. This element must
+				always be used in the context of a distribution, which is an application
+				within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - a									(a)
+				(m) - b									(b)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= (a + b) / 2
+				stdunc	= (b - a) / sqrt(8)
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distExponential" type="si:distExponentialType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				exponential distribution, which are used by METAS UncLib. This element must
+				always be used in the context of a distribution, which is an application
+				within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - mu								(mean)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= mu
+				stdunc	= mu
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distGamma" type="si:distGammaType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				gamma distribution, which are used by METAS UncLib. This element must
+				always be used in the context of a distribution, which is an application
+				within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - a									(shape)
+				(m) - b									(scale)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= a * b
+				stdunc	= (sqrt(a) * b
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distChiSquared" type="si:distChiSquaredType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				chi-squared distribution, which are used by METAS UncLib. This element must
+				always be used in the context of a distribution, which is an application
+				within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - k									(degrees of freedom)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= k
+				stdunc	= sqrt(2 * k)
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distStudentT" type="si:distStudentTType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				student T distribution, which are used by METAS UncLib. This element must
+				always be used in the context of a distribution, which is an application
+				within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - mu								(mean)
+				(m) - sigma								(standard deviation)
+				(m) - k									(degrees of freedom)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= mu for n > 2 with n = dof + 1
+				stdunc	= sigma * sqrt((n - 1) / (n - 3)) for n > 3 with n = dof + 1
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
+
+	<xs:element name="distStudentTFromSamples" type="si:distStudentTFromSamplesType">
+		<xs:annotation>
+			<xs:documentation xml:lang="en">
+				Definition of the structure, that gives the necessary components for stating 
+				student T distribution, which are used by METAS UncLib. This element must
+				always be used in the context of a distribution, which is an application
+				within si:uncInput.
+			</xs:documentation>
+			<xs:documentation xml:lang="en">
+				<![CDATA[
+				The element has the following components [(m)-mandatory, (o)-optional]:
+				 
+				(m) - samples							(samples)
+
+				The distributiom has the following mean value and standard uncertainty:
+
+				mean	= mean(samples) for n > 2 with n = dof + 1
+				stdunc	= sigma * sqrt((n - 1) / (n - 3)) for n > 3 with n = length(samples) and sigma = std(samples) / sqrt(n)
+				]]>
+			</xs:documentation>
+		</xs:annotation>
+	</xs:element>
 
 <!-- ############## D-SI XML TYPE DEFINITIONS #################### -->
 	
@@ -965,7 +1278,7 @@
 		</xs:complexType>
 
 		<xs:complexType name="uncDependenciesType">
-			<!-- the standard uncertainty can be computed on demand by taking the square root of the summed squared Jacobian values -->
+			<!-- the standard uncertainty can be computed on demand by taking the square root of the summed squared jacobi times input standard uncertainty values -->
 			<xs:sequence>
 				<xs:element minOccurs="0" maxOccurs="unbounded" name="dependency">
 					<xs:complexType>
@@ -982,6 +1295,8 @@
 			<xs:sequence>
 				<xs:element name="id" type="si:uncInputIdType" />
 				<xs:element name="label" type="xs:string" minOccurs="0" maxOccurs="1" />
+				<xs:element name="distribution" type="si:distributionType" />
+				<xs:element name="unit" type="si:unitType"/>
 			</xs:sequence>
 		</xs:complexType>
 
@@ -992,8 +1307,180 @@
 			</xs:restriction>
 		</xs:simpleType>
 		
-					
+		<xs:complexType name="distributionType" abstract="true"/>
+
+		<xs:complexType name="distStandardNormalType">
+			<!-- mu = 0, sigma = 1 -->
+			<!-- mean = mu -->
+			<!-- stdunc = sigma -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
 
+		<xs:complexType name="distNormalType">
+			<!-- mean = mu -->
+			<!-- stdunc = sigma -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="mu" type="si:decimalType" />
+						<xs:element name="sigma" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distStandardUniformType">
+			<!-- a = 0, b = 1 -->
+			<!-- mean = (a + b) / 2 -->
+			<!-- stdunc = (b - a) / sqrt(12) -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distUniformType">
+			<!-- mean = (a + b) / 2 -->
+			<!-- stdunc = (b - a) / sqrt(12) -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="a" type="si:decimalType" />
+						<xs:element name="b" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distCurvilinearTrapezoidType">
+			<!-- mean = (a + b) / 2 -->
+			<!-- stdunc = sqrt((b - a)^2 / 12 + d^2 / 9) -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="a" type="si:decimalType" />
+						<xs:element name="b" type="si:decimalType" />
+						<xs:element name="d" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distTrapezoidalType">
+			<!-- mean = (a + b) / 2 -->
+			<!-- stdunc = (b - a) * sqrt((1 + beta^2) / 24) -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="a" type="si:decimalType" />
+						<xs:element name="b" type="si:decimalType" />
+						<xs:element name="beta" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distTriangularType">
+			<!-- mean = (a + b) / 2 -->
+			<!-- stdunc = (b - a) / sqrt(24) -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="a" type="si:decimalType" />
+						<xs:element name="b" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distArcSineType">
+			<!-- mean = (a + b) / 2 -->
+			<!-- stdunc = (b - a) / sqrt(8) -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="a" type="si:decimalType" />
+						<xs:element name="b" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distExponentialType">
+			<!-- mean = mu -->
+			<!-- stdunc = mu -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="mu" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distGammaType">
+			<!-- mean = a * b -->
+			<!-- stdunc = sqrt(a) * b -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="a" type="si:decimalType" />
+						<xs:element name="b" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distChiSquaredType">
+			<!-- mean = k -->
+			<!-- stdunc = sqrt(2 * k) -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="k" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distStudentTType">
+			<!-- mean = mu for n > 2 with n = dof + 1 -->
+			<!-- stdunc = sigma * sqrt((n - 1) / (n - 3)) for n > 3 with n = dof + 1 -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="mu" type="si:decimalType" />
+						<xs:element name="sigma" type="si:decimalType" />
+						<xs:element name="dof" type="si:decimalType" />
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>
+
+		<xs:complexType name="distStudentTFromSamplesType">
+			<!-- mean = mean(samples) for n > 2 with n = dof + 1 -->
+			<!-- stdunc = sigma * sqrt((n - 1) / (n - 3)) for n > 3 with n = length(samples) and sigma = std(samples) / sqrt(n) -->
+			<xs:complexContent>
+				<xs:extension base="si:distributionType">
+					<xs:sequence>
+						<xs:element name="samples">
+							<xs:complexType>
+								<xs:sequence>
+									<xs:element minOccurs="0" maxOccurs="unbounded" name="sample" type="si:decimalType" />
+								</xs:sequence>
+							</xs:complexType>
+						</xs:element>
+					</xs:sequence>
+				</xs:extension>
+			</xs:complexContent>
+		</xs:complexType>