XSD - one of 2 attributes is required?

Is there a way to specify that one of 2 attributes is required in XSD?

for example, I have a definition like this:

<xs:attribute name="Name" type="xs:string" use="optional" />
<xs:attribute name="Id" type="xs:string" use="optional" />

I want to be able to define that at least one of these is required. Is that possible?

Solution 1:

No, I don't think you can do that with attributes. You could wrap two <xs:element> into a <xs:choice> - but for attributes, there's no equivalent construct, I'm afraid.

Solution 2:

XSD 1.1 will let you do this using asserts.

<xsd:element name="remove">
    <xsd:complexType>                        
        <xsd:attribute name="ref" use="optional"/>
        <xsd:attribute name="uri" use="optional"/>
        <xsd:assert test="(@ref and not(@uri)) or (not(@ref) and @uri)"/>            
    </xsd:complexType>
</xsd:element>

Solution 3:

Marc is quite right... You cannot have xs:attribute child elements inside a xs:choice parent element in XSD.

The logic seems to be that if two instances of an element have a mutually exclusive set of attributes then they are logically two different elements.

A workaround for this has been presented by Jeni Tennison here.

Solution 4:

You should look at this pages on W3C wiki: Simple attribute implication and Attribute muttex