Problem with restricting a W3C Schema Type

["Mark Seaborne" <MSeaborne@origoservices.com>]

Hi

I have got a complex type in a schema that looks like this:

<xsd:complexType name="Term">
	<xsd:sequence>
		<xsd:element name="years" minOccurs="0">
			<xsd:complexType>
				<xsd:simpleContent>
					<xsd:extension base="origo:SmallNumber">
						<xsd:attribute name="id" type="xsd:ID"/>
					</xsd:extension>
				</xsd:simpleContent>
			</xsd:complexType>
		</xsd:element>
		<xsd:element name="months" minOccurs="0">
			<xsd:complexType>
				<xsd:simpleContent>
					<xsd:extension base="origo:SmallNumber">
						<xsd:attribute name="id" type="xsd:ID"/>
					</xsd:extension>
				</xsd:simpleContent>
			</xsd:complexType>
		</xsd:element>
	<xsd:attribute name="id" type="xsd:ID"/>
</xsd:complexType>

I want to construct an element that restricts type "Term" to have only a "years" child element.

I am having problems getting this to work. 

If I remove the attribute "id" from the definition of "years", a restriction of "Term" works fine, but otherwise I get an error.

Any hints, or pointers to helpful documentation would be gratefully received.

All the best

Mark Seaborne

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