The 'publicid' NID is one that you can use with your domain name.

Start your namespace name with: urn:publicid:IDN+yourdomainhere.com:

The rest you make up with the following rules:

• Spaces become '+' (plus sign).

• '+' becomes %2B

• '/' becomes %2F

See RFC 3151 for more information.

For example, the namespace for my slide content is:

urn:publicid:IDN+mathdoc.org:schema:slides:2004:1.0:us