# Concurrent Computing with Shared Replicated Memory

## TL;DR

This paper models concurrent systems with shared replicated memory using concurrent ASM, analyzing different replication policies and messaging to understand their impact on system consistency.

## Contribution

It introduces a method to specify and analyze replicated memory management in concurrent systems using refined concurrent ASM models.

## Key findings

- Different replication policies affect system consistency.
- Messaging between data centers influences system behavior.
- Refined models help in understanding trade-offs in replication strategies.

## Abstract

The behavioural theory of concurrent systems states that any concurrent system can be captured by a behaviourally equivalent concurrent Abstract State Machine (cASM). While the theory in general assumes shared locations, it remains valid, if different agents can only interact via messages, i.e. sharing is restricted to mailboxes. There may even be a strict separation between memory managing agents and other agents that can only access the shared memory by sending query and update requests to the memory agents. This article is dedicated to an investigation of replicated data that is maintained by a memory management subsystem, whereas the replication neither appears in the requests nor in the corresponding answers. We show how the behaviour of a concurrent system with such a memory management can be specified using concurrent communicating ASMs. We provide several refinements of a high-level ground model addressing different replication policies and internal messaging between data centres. For all these refinements we analyse their effects on the runs such that decisions concerning the degree of consistency can be consciously made.