code: @Nonnull
    public static ValidationSource create (@Nullable final String sSystemID, @Nonnull final Node aNode)
    {
      ValueEnforcer.notNull (aNode, "Node");
      // Use the owner Document as fixed node
      return new ValidationSource (sSystemID, XMLHelper.getOwnerDocument (aNode), false);
    }
docs: Create a complete validation source from an existing DOM node.
  
  @param sSystemID
  System ID to use. May be <code>null</code>.
  @param aNode
  The node to use. May not be <code>null</code>.
  @return Never <code>null</code>.