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support for required attribute name aliases and/or attribute/attributeGroup choice In 1.1 you can achieve element name aliases: - substitution groups - <xs:choice> But none of this works on attributes where you want required attribute name to have an alias: <ELEMENT name="Some Element"> <ELEMENT caption="Some Element"> where "name" or "caption" should be specified. Another case is when you want to have alternative attributeGroups for an element with required ones included. Motivation: In my opinion this may by non rare case when you create schema for existing inconsistent XML documents ensuring backward compatibility or other motivations that bring substitution groups to elements. Anyway in my opinion similar capabilities should be available for elements and attributes.
This can be achieved in XSD 1.1 using assertions or using conditional type assignment. Using assertions: assert test="count((@name, @caption) eq 1)" Using CTA: alternative test="exists(@caption) != exists(@name)" type="..." alternative (other) type="xs:error There are no plans to produce a new version of XSD in the near future, so I think you will have to use one of these mechanisms for the foreseeable future.