Lépcsn

Lépcsn is a hypothetical construct used in discussions of event ordering in distributed computing and data streams. It is short for Local Event Pattern Correlation Sequence Number, a scalar metric intended to express how closely a locally observed event sequence aligns with a globally consistent order.

Definition and computation: Each processing node assigns a lépcsn to an emitted event. The value typically increases monotonically with local time and is updated when causal relationships are established. In practice, lépcsn values are compared across nodes to determine the likelihood that two events share a common causal past. The metric can be augmented with a tie-break rule using a monotone function of the local clock or a separate sequence counter.

Applications: Lépcsn is used in theoretical discussions about convergence guarantees for asynchronous event streams, conflict resolution in event sourcing, and the design of causal consistency models. It is often compared with vector clocks and Lamport timestamps as a lightweight approach for approximating causal order.

History and usage: The term originated in theoretical writings and classroom materials as a simplification of more complex ordering schemes. It is not a standard industry metric, but serves as a pedagogical tool to illustrate how local observations relate to global consistency in distributed systems.

See also: Related topics include vector clocks, Lamport timestamps, causal ordering, event sourcing, and CRDTs.