Why does SMIL Basic not use the SMIL namespace?

Why does SMIL Basic have its own XML namespace name?

XHTML Basic[XHTMB] use the XHTML namespace name, but has its own DTD. 

Should not a valid SMIL Basic document also be a valid SMIL 2.0 document?
With the solution in the working draft it will not.


[XHTMB] http://www.w3.org/MarkUp/Group/2000/PR-xhtml-basic-20000824/
--
Peter.Stark
@ecs.ericsson.se