Optional ReadonlydefaultOptional ReadonlylocalMatches the QName.localPart of the element. If undefined, this will match against
the property name from XmlRules.
Optional ReadonlynamespaceMatches the namespaceUri of the attribute.
If null, this will only match against a null namespace.
Note that attributes do not inherit default namespaces as elements do.
Optional ReadonlyrequiredIf true, a parsing error will be thrown if the value is undefined.
If the current element has no matching attribute, default will be used.