Rss/xml namespaces sgmllib, sax, minidom

[Sakcee]

I want to build a simple validator for rss2 feeds, that checks basic
structure and reports channels , items , and their attributes etc.

I have been reading Mark Pilgrims articles on xml.com, diveintopython
and someother stuff on sgmllib, sax.handlers and content handlers,
xml.dom.minidom

why is all of this necessary, what is the difference between all these
libraries, it seems to me that I can parse the rss2 feed with any of
these libraries.!! ?

what is the difference between namespaces and non-namspaces functions
in sax.handlers.contenthandler , is the namespace defined like domain
names on some website?

thanks for any comments