In one embodiment, a method includes receiving, by a server computing device, a notification which includes: information associated with the identity of the user associated with the user-initiated event or with the identity of the client computing device; a variable, pre-determined string of symbols for the user-initiated event associated with the notification; a variable number describing a value of an attribute associated with the user-initiated event; and a variable parameter describing an attribute of the user at or near the time of the event or an attribute of the variable number. The method includes correlating, by the server computing device, the user-initiated events with a user; and determining, by the computing device, a description of the user-initiated event associated with the notification based at least in part on the string of symbols.