Question

I’m trying to extend a complex type to change its minOccurs value, I tried different things unsuccessfully, here is my base type:

    <xs:complexType name="PhoneNumberType">
    <xs:sequence>
        <xs:element name="AreaCode">
            <xs:simpleType>
                <xs:restriction base="xs:string">
                    <xs:pattern value="[0-9]+" />
                    <xs:maxLength value="3" />
                </xs:restriction>
            </xs:simpleType>
        </xs:element>
        <xs:element name="LocalNumber">
            <xs:simpleType>
                <xs:restriction base="xs:string">
                    <xs:pattern value="[0-9]+" />
                    <xs:minLength value="7" />
                    <xs:maxLength value="17" />
                </xs:restriction>
            </xs:simpleType>
        </xs:element>
        <xs:element name="Extension" minOccurs="0">
            <xs:simpleType>
                <xs:restriction base="xs:string">
                    <xs:pattern value="[0-9]+" />
                    <xs:maxLength value="5" />
                </xs:restriction>
            </xs:simpleType>                
        </xs:element>
    </xs:sequence>
</xs:complexType>

First I tried this to make AreaCode optionnal for particular situations:

            <xs:element name="PhoneNumberWithOptionalAreaCode">
            <xs:complexType>
            <xs:complexContent>
                <xs:extension base="PhoneNumberType">
                    <xs:sequence>
                        <xs:element name="AreaCode" type="xs:string" minOccurs="0" />
                    </xs:sequence>
                </xs:extension>
            </xs:complexContent>
            </xs:complexType>
        </xs:element>

It gives me an error saying that elements with same name should have the same type.

So I tried this:

    <xs:complexType name="PhoneNumberType">
    <xs:sequence>
        <xs:element name="AreaCode" type="AreaCodeType" />
        <xs:element name="LocalNumber">
            <xs:simpleType>
                <xs:restriction base="xs:string">
                    <xs:pattern value="[0-9]+" />
                    <xs:minLength value="7" />
                    <xs:maxLength value="17" />
                </xs:restriction>
            </xs:simpleType>
        </xs:element>
        <xs:element name="Extension" minOccurs="0">
            <xs:simpleType>
                <xs:restriction base="xs:string">
                    <xs:pattern value="[0-9]+" />
                    <xs:maxLength value="5" />
                </xs:restriction>
            </xs:simpleType>                
        </xs:element>
    </xs:sequence>
</xs:complexType>

<xs:simpleType name="AreaCodeType">
    <xs:restriction base="xs:string">
        <xs:pattern value="[0-9]+" />
        <xs:maxLength value="3" />
    </xs:restriction>
</xs:simpleType>

    <xs:element name="PhoneNumberWithOptionalAreaCode">
        <xs:complexType>
        <xs:complexContent>
            <xs:extension base="PhoneNumberType">
                <xs:sequence>
                    <xs:element name="AreaCode" type="AreaCodeType" minOccurs="0" />
                </xs:sequence>
            </xs:extension>
        </xs:complexContent>
        </xs:complexType>
    </xs:element>

Now the xsd is valid, but when I try to validate the following xml it says LocalNumber is not expected, expected AreaCode.

<PhoneNumberWithOptionalAreaCode>
    <LocalNumber>1234567</LocalNumber>
</PhoneNumberWithOptionalAreaCode>

Can anyone help please ?

Thanks !

Answer 1

You cannot use neither extension/restriction to make a mandatory element optional in the lower hierarchy. See the XML Schema specification more on this:Restriction

Only possible solution would be invert the hierarchy if you have control. Make PhoneNumberWithOptionalAreaCode as base and have PhoneNumberType extend the PhoneNumberWithOptionalAreaCode