Design an operational semantics without global synchronization for Lambda-QC

Develop an operational semantics for the Quick Change choreographic calculus (Lambda-QC) that avoids global synchronization on choreographic function applications while preserving the intended behavior, and specify conditions under which this semantics remains correct with respect to endpoint projection.

Background

Lambda-QC adopts Pirouette’s out-of-order semantics, which requires all participants to synchronize on choreographic function applications. While this simplifies EPP correctness, it imposes a global synchronization barrier.

The authors note prior work attempting to use commuting conversions to eliminate such synchronization, but that approach is fragile in the presence of recursive functions and polymorphism. They therefore leave the task of finding a suitable semantics without global synchronization to future work.