About namespaces

[SwetaG@riskinc.com]

Hi,
I know how name spaces are used and how they are declared.The question that
comes to my mind is that how do i create the namespaces.

Like for the microsoft xdr schemas there is a namesapce called
urn:schemas-microsoft-com:xml-data where the things are defined.Basically
what is defined there..the schema tags and vocabulary or its sth else.

Suppose i want to create my own namespaces and want others to use the how
do i do it??for example i want that there are few elements say
<book>,<isbnno>,<author> and they are defied in name spaces.So how do i
define them first of all and then how do i create the namesapce so that
others can use them.

can anybody answer this question?

Regards,
Sweta