how to revert position of a jquery UI draggable based on condition

Question

I have an element which is draggable and an element which is droppable. Once the dragged item is dropped on the dropzone I am trying to execute the following jquery psuedo c

Answer 1

$("#droppable").droppable({ 
    accept: function(dropElem) {
        //dropElem was the dropped element, return true or false to accept/refuse it
        if($(this).data('stoneclass') == dropElem.attr("id")){
            return true;
    }
}
});​

This was used to accept only one draggable, from a group of draggables ; to one correct droppable, in a group of droppables.

P.S sorry for the language if it is not understandable =)