Universal Constructs in Distributed Computations

This paper presents two classes of universal constructs that occur in distributed computations and explores their properties. It first examines a pair of universal constructs termed IO and OI intervals that occur at nodes in distributed computations. These universal constructs are used as building blocks to design two global universal constructs, termed segments and paths, that occur across nodes in distributed computations. These constructs are a generalization of causal chains in a distributed computation. While a causal chain only captures the causal relation, it turns out that message chains in a distributed computation that do not capture causality play a significant role in the analysis of a distributed computation. We show that a number of key concepts and structures characterizing distributed computations are special cases of and can be expressed in terms of the two proposed constructs.