DOCBOOK: modifying the DocBook DTD

[Shang-Lin Chen]

If I modify the DocBook DTD, can I still use db2html to convert my DocBook
documents to HTML, or do I need to create my own parser? Would anyone know
where in the DTD to define an extension of cmdsynopsis? I'm trying to
study the DTD, and it seems a bit above my basic understanding of SGML.
Thanks!