An XmlResolver, which will be used while compiling and running queries, XPath expressions, and stylesheets, if no other XmlResolver is nominated
By default an XmlUrlResolver is used. This means that the responsibility
for resolving and dereferencing URIs rests with the .NET platform, not with the
GNU Classpath.
When Saxon invokes a user-written XmlResolver, the GetEntity method
may return any of: a System.IO.Stream; a System.IO.TextReader; or a
java.xml.transform.Source.