I have started a thread at the Adobe XMP forum to resolve questions wrt the PreservedFileName property of the XMP Media Managemenet schema.http://www.adobeforums.com/webx/.59b7e629
I've been using the XMP Toolkit SDK (v4.4.2, as of 2009/02/12), which can read and write XMP. Reading a property is pretty simple so there should be no problem to read the PreservedFileName property in an XMP packet.
I assume it's just as easy to write the property value too. However, the PreservedFileName property is not listed in the XMP Spec part 2 (the Media Management schema is described in Chap 2), but the XMP Toolkit does provide a way to extend the schema. The issue is whether the PreservedFileName property is officially part of that schema or not.