A unified semantic framework for window operators under late and out-of-order data

Dr Ahmed Awad, published a paper titled, ‘A unified semantic framework for window operators under late and out-of-order data’.

 

The growing adoption of stream processing engines (SPEs) has exposed critical inconsistencies in how window operators handle late and out-of-order events, undermining the portability, correctness, and maintainability of stream-based applications. We present a unified semantic framework centred on a window-operator lifecycle model that distinguishes single buffer and multi-buffer maintenance and semantic variations for event inclusion, recomputation, and result reporting. We instantiate the model on five widely used distributed SPEs, Apache Beam, Flink, Spark, Kafka Streams, and Storm, by mapping it to their APIs and execution behaviour, and run an identical windowed query under total-, partial-, and out of-order arrival. Even for one query over identical data, the engines diverge: under a total order, all differences reduce to two conventions (window-boundary inclusion and session-end labelling); a partial order adds order-dependent boundary counts that no fixed interval can justify (a window reported as 3 where only 2 or 4 are consistent); and out-of-order arrival splits the engines into context-aware versus context-agnostic session handling. We distil these findings into a portability checklist and a mapping of engine configuration knobs, giving developers a principled basis for configuring, testing, and porting window operators across SPEs.

 

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