A Document Architect's Perspective

This DTD stuff is great - mostly...

Hurray! XML makes it easy to describe flexible document structures, in a form that authors can use to create documents, designers can use to style them, and programmers can use to interpret them.
Oops! I said there were defaulted attributes! I guess XLink may not work then...
Er... I just modularised two parts of the DTD, but now I can't seem to make the rest of these documents use it
Uh... What are you doing to my design? You can't add elements in the internal subset like that! I know it said ANY, but that's for me to fill in, not you!