namespace is used for extending XML document that's define by another /
different people?

for example soap, someone defined soap envelope which is the basic structure
/ framework <HEADER>

then user of soap can add his own elements inside the framework --> inside
<HEADER> tag or

but the new user elements is defined by different people then soap envolpe,
so we need to have another namespace

is that the only reason why we need namespace? any other reason we need
namespace for each element?

Thanks