I have problem understanding the concept of Hazelcast Distributed Execution. It is said to be able to perform the execution on the owner instance of a specific key.
From Documentation:

   <T> Future<T> submitToKeyOwner(Callable<T> task, Object key)
   Submits task to owner of the specified key and returns a Future representing that task.
       Parameters:
            task - task
            key - key
       Returns:
            a Future representing pending completion of the task

I believe that I'm not alone to have a cluster built with multiple maps which might actually use the same key for different purposes, holding different objects (e.g. something along the following setup):

IMap<String, ObjectTypeA> firstMap = HazelcastInstance.getMap("firstMap");
IMap<String, ObjectTypeA_AppendixClass> secondMap = HazelcastInstance.getMap("secondMap");

To me it seems quite confusing what documentation says about the owner of a key. My real frustration is that I don't know WHICH - in which map - key does it refer to?
The documentation also gives a "demo" of this approach:

import com.hazelcast.core.Member;
import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.IExecutorService;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;   
import java.util.Set;
import com.hazelcast.config.Config;

public void echoOnTheMemberOwningTheKey(String input, Object key) throws Exception {
   Callable<String> task = new Echo(input);
   HazelcastInstance hz = Hazelcast.newHazelcastInstance();
   IExecutorService executorService = hz.getExecutorService("default");
   Future<String> future = executorService.submitToKeyOwner(task, key);
   String echoResult = future.get();
}

Here's a link to the documentation site: Hazelcast MultiHTML Documentation 3.0 - Distributed Execution
Did any of you guys figure out in the past what key does it want?