code: private String getElementURI() {
          String uri = null;
          // At this point in processing we have received all the
          // namespace mappings
          // As we still don't know the elements namespace,
          // we now figure it out.
  
          String prefix = getPrefixPart(m_elemContext.m_elementName);
  
          if (prefix == null) {
              // no prefix so lookup the URI of the default namespace
              uri = m_prefixMap.lookupNamespace("");
          } else {
              uri = m_prefixMap.lookupNamespace(prefix);
          }
          if (uri == null) {
              // We didn't find the namespace for the
              // prefix ... ouch, that shouldn't happen.
              // This is a hack, we really don't know
              // the namespace
              uri = EMPTYSTRING;
          }
  
          return uri;
      }
docs: Before this call m_elementContext.m_elementURI is null,
  which means it is not yet known. After this call it
  is non-null, but possibly "" meaning that it is in the
  default namespace.
  
  @return The URI of the element, never null, but possibly "".