Media types

TAG members,

The XML Protocol Working Group requests your input regarding media
types.  We've observed that some W3C working groups are registering
their own media types (including ourselves), and so had the
following questions about that;

Q. 1; What are the general guidelines or policies (if any) for W3C
working groups in defining their own media types?  Should they be
defining them at all?

Q. 2; If custom media types are required, should there be any
commonality between them?

Q. 3; What is, or what should be, the relationship between a media type
and an XML namespace?

Regards,

 The XML Protocol Working Group