This example shows how to handle XML Schema polymorphism features such
as xsi:type attributes and substitution groups in the C++/Parser mapping.
The case when xsi:type is used on root elements is covered in the
polyroot examples.

The example consists of the following files:

supermen.xsd
  XML Schema which describes the "supermen" instance documents.

supermen.xml
  Sample XML instance document.

supermen-pskel.hxx
supermen-pskel.cxx
  Parser skeletons generated by the XSD compiler from supermen.xsd.
  Note the use of the --generate-polymorphic command line option.

supermen-pimpl.hxx
supermen-pimpl.cxx
  Parser implementations that print the XML data to STDOUT.

driver.cxx
  Driver for the example. It first constructs a parser instance from
  all the individual parsers found in supermen-pimpl.hxx. It then invokes
  this parser instance to parse the input file.

To run the example on the sample XML instance document simply execute:

$ ./driver supermen.xml
