# Set-Constrained Delivery Broadcast: Definition, Abstraction Power, and Computability Limits

## TL;DR

This paper introduces the SCD-broadcast abstraction for asynchronous message-passing systems, demonstrating its implementation, programming power, and limits, including equivalence to read/write registers.

## Contribution

It defines SCD-broadcast, provides an implementation, and analyzes its computational power and limitations in distributed systems.

## Key findings

- SCD-broadcast enables simple, efficient algorithms for distributed objects.
- SCD-broadcast-based algorithms can implement snapshot and conflict-free replicated data.
- SCD-broadcast is computationally equivalent to read/write registers.

## Abstract

This paper introduces a new communication abstraction, called Set-Constrained Delivery Broadcast (SCD-broadcast), whose aim is to provide its users with an appropriate abstraction level when they have to implement objects or distributed tasks in an asynchronous message-passing system prone to process crash failures. This abstraction allows each process to broadcast messages and deliver a sequence of sets of messages in such a way that, if a process delivers a set of messages including a message m and later delivers a set of messages including a message m ' , no process delivers first a set of messages including m ' and later a set of message including m. After having presented an algorithm implementing SCD-broadcast, the paper investigates its programming power and its computability limits. On the "power" side it presents SCD-broadcast-based algorithms, which are both simple and efficient, building objects (such as snapshot and conflict-free replicated data), and distributed tasks. On the "computability limits" side it shows that SCD-broadcast and read/write registers are computationally equivalent.

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Source: https://tomesphere.com/paper/1706.05267