How to ensure empty XML tag still contains the parent key?

Question

I have a relationship between a parent Foo and its child Bar. When Bar contains anything within it, then it is mapped into a table containing the child-key column "FooID".

For instance, if the XML contains:

<Bar>
    <Anything/>
</Bar>

then the FooID column will be populated.

|FooID|OtherColumns |...|
|--| --- | --- |
|FooID_1 |  | |

However, my problem is that when Bar is empty or a self closing tag, then FooID is not populated. Is there a way to make a change from within the XML so that the child-key is set on the child even if the child is empty?

Current problematic functionality:

<Bar></Bar>
    OR
<Bar/>

results in:

|FooID|OtherColumns |...|
|--| --- | --- |
| |  | |

My .XSD:

<sql:relationship name="Foo_Bar" parent="Foo" parent-key="id" child="Bar" child-key="FooID"/>
<xsd:element name="Foo" sql:relation="Foo" sql:relationship="SomeRel_Foo">
    <xsd:complexType>
        <xsd:sequence>
            ...
            <xsd:element name="Bar" sql:relation="Bar" sql:relationship="Foo_Bar">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element name="SomeElement1" type="xsd:string"/>
                        <xsd:element name="SomeElement2" type="xsd:string"/>
                    </xsd:sequence>
                    <xsd:attribute name="id" type="xsd:string"/>
                    <xsd:attribute name="FooID" type="xsd:string"/>
                </xsd:complexType>
            </xsd:element>
            ...

UPDATE:

I also tried the following:

<xsd:attribute name="FooID" type="xsd:string" use="required"/>  
     AND  
<xsd:element minOccurs="0" name="OrgForm" type="xsd:string" />