Now you've seen that qnames occur all over the place.
Those prefixes must be declared:
On the current element or nearest ancestor there must exist a namespace declaration attribute that uses that prefix.
A namespace declaration attribute consists of an attribute that starts with the special prefix 'xmlns' followed by a colon ':' and the prefix being declared.
The value of the attribute is an absolute URI that declares the namespace.
You can default the namespace for elements by excluding the prefix in the declaration.
Defaults are "in scope" for their children.
When a default is present, element names with no prefix use that namespace.
Attributes do not use the default namespace.