Common use of Safety properties Clause in Contracts

Safety properties. ‌ Observation 1. Given any correct process pj its SvS contains at most one value for each process in P. The above observation derives from the specification of reliable broadcast, and the fact that in the disclosure phase each participating process broadcasts a single value. We say that a message m containing a set of proposed values is “safe” for a process pi if such set of values is contained in SvS. It is immediate from function at Lines 35-39 that proposers (in state proposing) change their Proposed set only when they receive safe messages. The analogous holds for the Accepted set of acceptors. We say that a value v receives m acks if it is contained in a Proposed set, that is in turn contained in ack messages in the form < ack, , ts > sent by m acceptors. The same meaning is intended when we say that Proposed set receives acks. Algorithm 1 WTS (Wait Till Safe) -Algorithm for Proposer process pi 1: proposed value = proi