XSD - one of 2 attributes is required?
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>
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.