A programmatic mechanism for alerting interested recipients (observers) that some event has occurred during program execution. The observers can be users, other processes, or even the same process that originates the notification. In Mac OS X, the term is used to identify specific mechanisms that are variations of the basic meaning. In the kernel environment, notification is sometimes used to identify a message sent via IPC from kernel space to user space. Distributed notifications provide a way for a process to broadcast an alert (along with additional data) to any other process that makes itself an observer of that notification. Finally, the Notification Manager (a Carbon manager) lets background programs notify users—through blinking icons in the menu bar, by sounds, or by dialogs—that their intercession is required. In Enterprise Objects, it’s a mechanism that provides an asynchronous communication infrastructure between objects.