XML is just the syntax in which we encode document models... what really matters is how we modeled the documents
The essence of Document Engineering is the analysis and design methods that yield formal models that describe the information that business processes or services require
Doing business requires both "publication-like" document types like brochures and technical manuals and "transactional" documents like purchase orders and invoices – so we need analysis and design methods that work for both ends of this "Document Type Spectrum"