code: public static QName tagToQName(final String tag,
  			final Map<String, String> nsRegistry) {
  		final String[] split = tag.split("\\:");
  
  		if (split.length <= 1) {
  			return new QName(split[0]);
  		} else {
  			final String namespace = nsRegistry.get(split[0]);
  
  			if (namespace != null) {
  				return new QName(namespace, split[1]);
  			} else {
  				return new QName(split[1]);
  			}
  		}
  	}
docs: Transform a tag, local or prefixed with a namespace alias, to a local or
  full QName.
  
  @param tag
  The tag to convert, it can be local like <code>azerty</code>
  or qualified like <code>ns1:azerty</code>.
  @param nsRegistry
  The namespaces registry containing for an alias, the full
  namespace name.
  @return the QName corresponding to the tag, it will be a local QName
  except if a prefix was provided and it could be found in the
  namespace registry.