Only drag when clicking a parent element, not its children

I'm using jquery-ui to let my div element be draggable. It looks like this:

<div id="parent">
   <div id="child">
      //here is some stuff like tabs and other dynamic content
   </div>
</div>

So the parent is draggable and I can drag whole element even if I drag on the space which is occupy by element with the id "child". I don't want drag when clicking the child element

In other words:

I want make my parent to be a natural draggable frame for its child elements, but this child must not trigger the parent draggable too.