WIP on an Object.defineProperty() facade for YUI (as an alternative to Y.Attribute)

property-base.js

function Property() {}

Property.prototype = {
    // -- Public Prototype Methods ---------------------------------------------
    defineProperties: function (properties) {
        return Property.defineProperties(this, properties);
    },

    defineProperty: function (name, descriptor) {
        return Property.defineProperty(this, name, descriptor);
    },

    get: function (name) {
        return this[name];
    },

    getProperties: function (names) {
        var properties = {},
            i, len, name;

        for (i = 0, len = names.length; i < len; i++) {
            name = names[i];
            result[name] = this.get(name);
        }

        return properties;
    },

    set: function (name, value) {
        return this[name] = value;
    },

    setProperties: function (properties, options) {
        for (var name in properties) {
            if (properties.hasOwnProperty(name)) {
                this.set(name, properties[name], options);
            }
        }
    }
};

// -- Static Methods -----------------------------------------------------------
Property.defineProperties = function () {
    return Object.defineProperties.apply(null, arguments);
};

Property.defineProperty = function () {
    return Object.defineProperty.apply(null, arguments);
};

Y.Property = Property;

property-events.js

var oldSet = Y.Property.prototype.set;

Y.augment(Y.Property, Y.EventTarget);

Y.Property.prototype.set = function (name, value, options) {
    var prevVal = this.get(name),
        newVal  = oldSet.call(this, name, value, options);

    this.fire(name + 'Change', Y.merge(options, {
        newVal      : newVal,
        prevVal     : prevVal,
        propertyName: name
    }));

    return newVal;
};