DS.attr = function(type, options) {
  var transform = DS.attr.transforms[type];
  ember_assert("Could not find model attribute of type " + type, !!transform);

  var transformFrom = transform.from;
  var transformTo = transform.to;

  options = options || {};

  var meta = { type: type, isAttribute: true, options: options };

  return Ember.computed(function(key, value) {
    var data;

    key = options.key || key;

    if (arguments.length === 2) {
      value = transformTo(value);
      this.setProperty(key, value);
    } else {
      data = get(this, 'data');
      value = get(data, key);

      if (value === undefined) {
        if($.isFunction(options.defaultValue)) {
          value = options.defaultValue();
        } else {
          value = options.defaultValue;
        }
      }
    }

    return transformFrom(value);
  // `data` is never set directly. However, it may be
  // invalidated from the state manager's setData
  // event.
  }).property('data').cacheable().meta(meta);
};