[Zope] Is DTML a bastardized form of XML, or valid XML?

Hi, just wondering if DTML is actually a valid form of XML, or a bastardized version of XML created specifically for ZOPE. I've done a little reasearch on XML, and I it seems like DTML tags such as: <dtml-var "..."> or <dtml-if "..."> ... <dtml-else> ... </dtml-if> aren't really valid XML forms. The following would make more sense: <dtml-var expr="..."/> or <dtml-if expr="..."> ... <dtml-else> ... </dtml-else> ... </dtml-if> Anyone care to enlighten me? Thanks, kh