https://xalan.apache.org/old/xalan-j/apidocs/org/apache/xml/utils/XMLString.html
Xalan-Java 2.7.1: Interface XMLString
javainterface
https://xmlbeans.apache.org/docs/5.0.0/org/apache/xmlbeans/XmlString.html
XmlString (XMLBeans 5.0.1 Documentation)
declaration: package: org.apache.xmlbeans, interface: XmlString
documentation