An Enhanced Exchange Operator for XC

Recent work in the area of coordination models and collective adaptive systems promotes a view of distributed computations as functions manipulating computational fields (data structures spread over space and evolving over time) and introduces the eXchange Calculus (XC) as a novel formal foundation for field computations. In XC, evolution (time) and neighbor interaction (space) are handled by a single communication primitive called exchange, working on the neighbouring value data structure to represent both received values and values to share. However, the exchange primitive does not allow to directly retain information about neighbours across subsequent rounds of computation. This hampers the convenient expression of useful algorithms in XC, such as the computation of a neighbour reliability score. In this paper, we introduce a new generalised version of the exchange primitive, also implementing it into the FCPP DSL. This primitive allows for neighbour data retention across rounds, strictly expanding the expressiveness of the exchange primitive in XC. The contribution is then evaluated through a case study on distributed sensing in a wireless sensor network of battery-powered devices, exploiting the reliability scores to improve robustness.