Within the XML Schema (XSD) 1.1 specification, xs:assertion is defined to say that it can have an optional xpathDefaultNamespace attribute.

Can anyone please, share a sample use case, where the xpathDefaultNamespace attribute on xs:assertion is required and useful?

Is an optional xs:annotation child of xs:assertion, can make use of xpathDefaultNamespace attribute on xs:assertion, or is there any other use case of having xpathDefaultNamespace attribute on xs:assertion?  

 
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