Add annotation-documentation to XSD child element

Question

I want to add an annotation-documentation to a XSD child element:

For example:

<xsd:complexType name="XY">
    <xsd:sequence>
        <xsd:element type="xType" name="x"/>
            <xsd:annotation>
                <xsd:documentation> I want to add a description here. 
                </xsd:documentation>
            </xsd:annotation>
        <xsd:element type="yType" name="y"/>
    </xsd:sequence>
    <xsd:attribute type="xsd:string" name="NAME" use="required"/>
</xsd:complexType>

does obviously not work.

Is there a way to explicitly define a documentation of just the child element

Answer 1

Don't tell us it doesn't work, tell us how it fails!

I can't see any reason your code should fail (let alone any "obvious" reason). Of course, it contains references to undeclared types. The following example works just fine:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
    
    <xs:element name="X">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="a" type="xs:string">
                    <xs:annotation>
                        <xs:documentation>Great!</xs:documentation>
                    </xs:annotation>
                </xs:element>
            </xs:sequence>
            <xs:assert test="matches(a, '^(hello|world)$', 'm')"/>                                           
        </xs:complexType>
    </xs:element>
    
</xs:schema>