Implications of this Breakdown

A Need for More Flexible Parsers

Not Your Mother's XML 1.0 Although the documents used by XPDL are XML 1.0 documents and may be processed by XML 1.0 parsers, more sophisticated tools (basically equipped with on/off switches) are needed for XPDL processing.
Wishing for a Layered Model XML 1.0 left processing as the responsibility of a single large processor that had its own options. Converting these tools to an XPDL approach may require some heavy retrofitting.
Legacies We still need to figure out how to deal with old-style DOCTYPEs and their content. Entities in particular are often document-specific.