code: public XAttributeNameMap getMapping(String name) {
  		XAttributeNameMapImpl mapping = mappings.get(name);
  		if(mapping == null) {
  			mapping = new XAttributeNameMapImpl(name);
  			mappings.put(name, mapping);
  		}
  		return mapping;
  	}
docs: Provides access to a specific attribute name
  mapping by its name. If the requested mapping does
  not exist yet, a new mapping will be created, added
  to the set of managed mappings, and returned. This
  means, this method will always return a mapping,
  but this could be empty.
  
  @param name Name of the requested mapping.
  @return The requested mapping, as stored in this
  facility (or newly created).