Wow, there's really not that much on the web about this. Fortunately, it's
not hard to understand, so here goes.

This is the start of an InfoPath XML file with the PIs that you should worry
about

<!-- Standard PI for any XML file. InfoPath currently reads only UTF-8
encoding -->
<?xml version="1.0" encoding="UTF-8"?>

<!-- Information about the solution location and version
   solutionVersion in the XML and XSF files must match
   PIVersion - Currently at 1.0.0.0 for all versions of InfoPath
   href - tells InfoPath where to find the form template that edits this
XML. For ease of explanation, I won't talk about the urn attribute
   name - must match between the XSF and the XML. Simply a unique name for
this form
   productVersion - tells what version of InfoPath created this form
<?mso-infoPathSolution solutionVersion="1.0.0.7" PIVersion="1.0.0.0"
href="http://dummy/myForm.xsn"
name="urn:schemas-microsoft-com:office:infopath:ipxbox:-dataFormSolution"
productVersion="11.0.6255" ?>

<!-- mso-application is used by the various Office applications when writing
XML files.
It allows XML to be opened by the correct application when downloaded in a
web browser
or double-clicked in Windows Explorer." -->
<?mso-application progid="InfoPath.Document"?>

Thanks,
Brian