docs: function(elName, url, attr) {
           var node = this.createElementDefaultNS(elName);
           node.appendChild(this.write_wmc_OnlineResource(url));
           if (attr) {
               var optionalAttributes = ["width", "height", "format"];
               for (var i=0; i<optionalAttributes.length; i++) {
                   if (optionalAttributes[i] in attr) {
                       node.setAttribute(optionalAttributes[i], attr[optionalAttributes[i]]);
                   }
               }
           }
           return node;
       }