Schema: String Type
XML Schema
<xsd:attribute name=“at”
     type=“xsd:string”>
Doesn’t validate with xsd:string type.
“The ·value space· of string is the set of finite-length sequences of characters (as defined in [XML 1.0 (Second Edition)]) that ·match· the Char production from [XML 1.0 (Second Edition)].”  (XML Schema Part 2)
at=“&#x1f”