These alias will be declared at the root level in the document.
The sample shows what you get if an alias “MyAlias”, and UIR "http://sample" are added to the collection.

<?xml version="1.0"?>
<MyAlias:Customer xmlns:MyAlias="http://sample"
xmlns:xs="http://www.w3.org/2001/XMLSchema-instance"
clubCardMember="false">

Also See AliasNamespaceDictionary

public class AliasNamespaceDictionary {
    public String getNamespaceURI(String nsAlias);
    public java.util.Set getAliases();
    public java.util.Collection getNamespaces();
    public void add(String nsAlias, String namespaceUri);
    public boolean contains(String nsAlias);
    public void remove(String nsAlias);
}