"Futures" When we send a request to an active object, sometimes we want to know when the request was processed, and get the result of the processing. For example, we could have an active object that performs DNS queries, and we want to get the reply of the query. One way is to pass a callback function with the request, and have the active object invoke it when its done processing. This will get the reply's processing, however, in the context of the active object's internal thread. Another way is to pass a 'Future' object to the active object, and have an API allowing the active object to set the reply in the 'future' object, and for us to extract the reply from the 'Future' object.