Often it is useful to have the server notify the client of an event. This is not usually possible in a web environment, where all communication follows the pattern of client request followed by server response. Dekho utilizes a messaging technology to allow the server to “push” messages to the clients. This allows external customizations to, for example, manipulate the current session details such as the selection or the map, then send a message to the client to notify it that the session details have changed. Using the messaging technology, the client is able to react immediately.