On the Semantic Overlap of Operators in Stream Processing Engines

Stream Processing Engines (SPEs) extract value from data streams in the Edge-to-Cloud continuum through graphs of operators that progressively transform data. State-of-the-art SPEs are bridged into shared models based on their overlapping APIs. The overlap in their semantic expressiveness, though, goes beyond their APIs and can be formally assessed by distilling the semantics they support into minimal sets of operators, and by checking whether such sets overlap. As we show, stream Aggregates suffice to enforce the semantics of other common operators. Moreover, compositions of Aggregates can match the performance of other operators in state-of-the-art SPEs, and micro-SPEs building on a single Aggregate operator can even surpass other SPEs’ performance while holding the same semantic expressiveness with a minimal code footprint. Our approach lays down new analytical findings with practical implications in minimizing the operational effort to use SPEs, especially at the edge, while seamlessly benefiting existing distribution/parallelization techniques.