All namespaces are stored at GXml.Node.namespaces owned by this GXml.TDocument.
First namespace at list, is considered default one for the document. If you haven't declared a namespace for this document or for its root element, and you define one for a child node, this one is added for the first time to document's namespaces, then this becomes the default namespace. To avoid this, you should set a namespace for documento or its root, then children.
Default GXml.Namespace for a document is the first