Step 3: Session Windows

Unlike fixed time buckets, a session window groups events until the configured inactivity period is reached.

The boundary can represent a user interaction period or a sensor activity period when its source semantics support that interpretation.

Session boundary

An inactivity-based session would group events until a configured gap occurs. It needs explicit state, per-key timeouts, and rules for late or out-of-order events.

The maintained complete aggregation configuration implements fixed and sliding windows, not inactivity sessions. group_by_value groups an existing batch; it does not maintain per-sensor inactivity timers.

A session implementation and its regression coverage must be supplied separately before this concept can be treated as an executable pipeline.