A mapping from
client-side zone ids to objects that can render the content for that zone on the client. An event handler method may instantiate an instance and chain together a series of calls to {@link #add(String,Object)}, and return the final result.
Remember that client-side element ids may not match server-side component ids, especially once Ajax is added to the mix. Because of this, it is highly recommended that the client-side logic gather the actual component ids and include those in the Ajax request, to ensure that the server generates updates that the client can process. Better yet, use the Zone's id parameter to lock down the zone's id to a known, predictable value.
@since 5.1.0.1