Eventsalso

Eventsalso is a term used in discussions of event-driven programming to describe a coordination pattern that treats events from multiple sources as part of a connected system. The idea is to observe several event streams and apply rules that account for events occurring across streams, enabling actions that depend on more than a single source. The term is primarily descriptive and not tied to a formal specification, but it conveys the notion of cross-stream awareness and parallel handling.

Semantics and implementation: In an eventsalso pattern, a coordination layer receives annotated events from various sources, groups them by time, key, or context, and applies a set of “also” rules such as joint triggering, correlation, or window-based joining. Observers can subscribe to the composite stream or to individual outputs produced by the coordination logic. Implementations may deploy synchronous or asynchronous processing, and may incorporate backpressure, deduplication, and fault tolerance.

Use cases: In user interfaces, events from multiple controls may need to be reflected together. In distributed systems, events from services can be correlated to infer higher-level state. In data processing, streams can be joined by timestamps or keys to produce unified records. Advantages include richer context and faster cross-source responses; drawbacks include increased design complexity and the risk of race conditions if timing is not carefully managed.

Status: The term is informal and not widely standardized. It appears in some technical discussions as a shorthand for multi-stream coordination patterns. Related concepts include event-driven architecture, reactive programming, complex event processing, and stream joins.