Event-Driven Programming as a Way to Unify Control Statements

Abstract

Event-driven programming (EDP) is a programming paradigm in which actions are performed after notification of an event. The paradigm can be used to unify control statements (as in Markov normal algorithms). Unification consists in using only a linear sequence of commands when programming events and their handlers. We introduce a new look at EDP. Event-driven architecture (EDA) for our look includes a framework, events and their handlers. The framework consists of an event queue and its dispatcher, event loop handlers as threads. EDA has the following features: one input event is transformed into one output event, one event is processed by one handler and vice versa, subscription to an event by its type, handler searching by event parameters, queue with a broker, data exchange between handlers through events. The event is characterized by a type, input data, a status, the parent event, a processing result. The handler processes the event, filters processed events, and provides a reference to the subscribed event type. The resolving handler transforms the initiated event into a handled one. The transformation handler initiates a new event in place of the handled one. EDA is thread-safe due to storing state only in events, stateless handlers, using a thread-safe queue, sequentially processing events one after another. EDA was programmed in Java. The program includes 3 loop statements (including 1 in the thread pool) and 4 conditional statements. All these statements are in the framework. Only a linear sequence of commands is used in events and handlers.