/**
                            * Extends IO to enable HTML form data serialization, when specified
                            * in the transaction's configuration object.
                            * @module io
                            * @submodule io-form
                            * @for IO
                            */
                            
                            var eUC = encodeURIComponent;
                            
                            /**
                             * Enumerate through an HTML form's elements collection
                             * and return a string comprised of key-value pairs.
                             *
                             * @method stringify
                             * @static
                             * @param {Node|String} form YUI form node or HTML form id
                             * @param {Object} [options] Configuration options.
                             * @param {Boolean} [options.useDisabled=false] Whether to include disabled fields.
                             * @param {Object|String} [options.extra] Extra values to include. May be a query string or an object with key/value pairs.
                             * @return {String}
                             */
                            Y.IO.stringify = function(form, options) {
                                options = options || {};
                            
                                var s = Y.IO.prototype._serialize({
                                    id: form,
                                    useDisabled: options.useDisabled
                                },
                                options.extra && typeof options.extra === 'object' ? Y.QueryString.stringify(options.extra) : options.extra);
                            
                                return s;
                            };
                            
                            Y.mix(Y.IO.prototype, {
                               /**
                                * Enumerate through an HTML form's elements collection
                                * and return a string comprised of key-value pairs.
                                *
                                * @method _serialize
                                * @private
                                * @param {Object} c
                                * @param {String|Element} c.id YUI form node or HTML form id
                                * @param {Boolean} c.useDisabled `true` to include disabled fields
                                * @param {String} s Key-value data defined in the configuration object.
                                * @return {String}
                                */
                                _serialize: function(c, s) {
                                    var data = [],
                                        df = c.useDisabled || false,
                                        item = 0,
                                        id = (typeof c.id === 'string') ? c.id : c.id.getAttribute('id'),
                                        e, f, n, v, d, i, il, j, jl, o;
                            
                                    if (!id) {
                                        id = Y.guid('io:');
                                        c.id.setAttribute('id', id);
                                    }
                            
                                    f = Y.config.doc.getElementById(id);
                            
                                    if (!f || !f.elements) {
                                        return s || '';
                                    }
                            
                                    // Iterate over the form elements collection to construct the
                                    // label-value pairs.
                                    for (i = 0, il = f.elements.length; i < il; ++i) {
                                        e = f.elements[i];
                                        d = e.disabled;
                                        n = e.name;
                            
                                        if (df ? n : n && !d) {
                                            n = eUC(n) + '=';
                                            v = eUC(e.value);
                            
                                            switch (e.type) {
                                                // Safari, Opera, FF all default options.value from .text if
                                                // value attribute not specified in markup
                                                case 'select-one':
                                                    if (e.selectedIndex > -1) {
                                                        o = e.options[e.selectedIndex];
                                                        data[item++] = n + eUC(o.attributes.value && o.attributes.value.specified ? o.value : o.text);
                                                    }
                                                    break;
                                                case 'select-multiple':
                                                    if (e.selectedIndex > -1) {
                                                        for (j = e.selectedIndex, jl = e.options.length; j < jl; ++j) {
                                                            o = e.options[j];
                                                            if (o.selected) {
                                                              data[item++] = n + eUC(o.attributes.value && o.attributes.value.specified ? o.value : o.text);
                                                            }
                                                        }
                                                    }
                                                    break;
                                                case 'radio':
                                                case 'checkbox':
                                                    if (e.checked) {
                                                        data[item++] = n + v;
                                                    }
                                                    break;
                                                case 'file':
                                                    // stub case as XMLHttpRequest will only send the file path as a string.
                                                case undefined:
                                                    // stub case for fieldset element which returns undefined.
                                                case 'reset':
                                                    // stub case for input type reset button.
                                                case 'button':
                                                    // stub case for input type button elements.
                                                    break;
                                                case 'submit':
                                                default:
                                                    data[item++] = n + v;
                                            }
                                        }
                                    }
                            
                                    if (s) {
                                        data[item++] = s;
                                    }
                            
                                    Y.log('HTML form serialized. The value is: ' + data.join('&'), 'info', 'io');
                                    return data.join('&');
                                }
                            }, true);