A namespace container may be associated with a default namespace. This is specified in the properties of the namespace container. To access these properties, in the Repository navigator select the namespace container and then right click and select Properties.
The default namespace is only used on the output side of the map and causes the emitted XML to use an xmlns attribute with no namespace prefix and a value of the specified default namespace URL for the root element of the output document. This sets the namespace URI for all enclosing elements to be that of the default namespace URI without need for a namespace prefix on each element. In the event that there are multiple namespace containers used in the output structure of the map, only the first specified default namespace is used.