In our example, we have two such declarations:
xmlns:xs="http://www.w3.org/2001/XMLSchema"
and
xmlns:lib="http://dyomedea.com/ns/library".
The first declaration associates the W3C XML Schema namespace with
the prefix xs. We could, of course, have chosen
any prefix, or even used this namespace as the default namespace; the
choice of xs is just common usage.
The second declaration defines the namespace used in our instance
document,
xmlns:lib="http://dyomedea.com/ns/library".
Here we chose to use the lib prefix, even though
this namespace is never used for any element or attribute of the
schema itself. We could also have chosen any prefix for this
namespace, or even have defined it as our default namespace.