Cannot generate ABAP proxy

Hi,

I am getting the following error message while I am trying to generate an ABAP proxy:

Cannot generate proxy (object <element name="SubstanceComponent"> missing in WSDL, see long text)

I did the following steps:

<i>1) Import an External Definition from an XSD-File:</i>

<?xml version="1.0" encoding="ISO-8859-1"?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
	<xs:simpleType name="Num4Dec">
		<xs:annotation>
			<xs:documentation>
			Decimal Number with 4 fractional digits
			</xs:documentation>
		</xs:annotation>
		<xs:restriction base="xs:decimal">
			<xs:fractionDigits value="4" />
		</xs:restriction>
	</xs:simpleType>
	<xs:element name="SubstanceComponent">
		<xs:complexType>
			<xs:sequence minOccurs="0" maxOccurs="unbounded">
				<xs:element ref="SubstanceComponent" />
			</xs:sequence>
			<xs:attribute name="localIDRef" type="xs:string" use="required">
				<xs:annotation>
					<xs:documentation>
					Reference on details in ProductComponents
					</xs:documentation>
				</xs:annotation>
			</xs:attribute>
			<xs:attribute name="type" use="required">
				<xs:annotation>
					<xs:documentation>
					Role of the item in the composition
					</xs:documentation>
				</xs:annotation>
				<xs:simpleType>
					<xs:restriction base="xs:string">
						<xs:enumeration value="default" />
						<xs:enumeration value="rest" />
						<xs:enumeration value="impurity" />
					</xs:restriction>
				</xs:simpleType>
			</xs:attribute>
			<xs:attribute name="value" type="Num4Dec" />
			<xs:attribute name="valueLower" type="Num4Dec" />
			<xs:attribute name="valueUpper" type="Num4Dec" />
			<xs:attribute name="isoUnit">
				<xs:simpleType>
					<xs:restriction base="xs:string">
						<xs:enumeration value="%" />
						<xs:enumeration value="ppm" />
					</xs:restriction>
				</xs:simpleType>
			</xs:attribute>
			<xs:attribute name="description" type="xs:string">
				<xs:annotation>
					<xs:documentation>
					Descritpive Name for visualization
					</xs:documentation>
				</xs:annotation>
			</xs:attribute>
			<xs:attribute name="intentionallyAdded" type="xs:boolean">
				<xs:annotation>
					<xs:documentation>
					intentionally added according to JIG
					</xs:documentation>
				</xs:annotation>
			</xs:attribute>
		</xs:complexType>
	</xs:element>
</xs:schema>

<i>2) Create a Message Interface based on the External Definition

3) Trying to generate the ABAP proxy...

</i>

Do you have any idea why the proxy generation is not working in this case? Is it the recursive use of element "SubstanceComponent" that doesn't work?

<xs:element name="SubstanceComponent">
		<xs:complexType>
			<xs:sequence minOccurs="0" maxOccurs="unbounded">
				<xs:element ref="SubstanceComponent" />
			</xs:sequence>

Thanks,

Andreas