# The confusing CAP and ACID wording

DevFeed: [The confusing CAP and ACID wording](<https://devfeed.tech/articles/the-confusing-cap-and-acid-wording-21687.md>)

Original publisher: [Read original article](<http://blog.thislongrun.com/2015/03/the-confusing-cap-and-acid-wording.html>)

Author: Nicolas Liochon (noreply@blogger.com)

Published: 2015-03-26T15:30:00Z

Content type: article

Language: en

Sources: [Nicolas Liochon](<https://devfeed.tech/sources/nicolas-liochon.md>)

Topics: [distributed-systems](<https://devfeed.tech/topics/distributed-systems.md>), [Databases](<https://devfeed.tech/topics/databases.md>), [Transactions](<https://devfeed.tech/topics/transactions.md>), [integrity](<https://devfeed.tech/topics/integrity.md>)

Tags: [acid](<https://devfeed.tech/tags/acid.md>), [availability](<https://devfeed.tech/tags/availability.md>), [cap-theorem](<https://devfeed.tech/tags/cap-theorem.md>), [consistency](<https://devfeed.tech/tags/consistency.md>), [database](<https://devfeed.tech/tags/database.md>), [distributed-system](<https://devfeed.tech/tags/distributed-system.md>), [distributed-systems](<https://devfeed.tech/tags/distributed-systems.md>), [durability](<https://devfeed.tech/tags/durability.md>), [integrity](<https://devfeed.tech/tags/integrity.md>), [latency](<https://devfeed.tech/tags/latency.md>), [network](<https://devfeed.tech/tags/network.md>), [partition](<https://devfeed.tech/tags/partition.md>), [properties](<https://devfeed.tech/tags/properties.md>), [systems](<https://devfeed.tech/tags/systems.md>), [transactions](<https://devfeed.tech/tags/transactions.md>)

## AI overview

This article explains why CAP and ACID use overlapping terms with different meanings in distributed systems and database systems. It compares concepts including consistency, atomicity, transactions, durability, availability, and partition tolerance, highlighting where the terminology overlaps and where the concepts differ.

## Source excerpt

CAP and ACID share a common vocabulary: Atomic, Consistent, and so on. But there is a catch: the words are the same but they mean totally different things. CAP comes from the distributed systems theory, while ACID belongs to database systems one.The Distributed Databases use both CAP and ACID vocabulary, so this obviously creates a lot of confusion. When someone says: "one should not give up consistency" what's the consistency he is speaking about? Let's have a look at the definitions of Atomic-Consistent-Isolated-Durable and Consistent-Available-Partition-tolerant. ACID & CAP - A reminder ACID properties were identified in the 70's, then the term ACID was coined in 1983. We have: A for Atomicity C for Consistency I for for Isolation D for Durability Reminder: the ACID properties were defined in California during the 70's. The CAP theorem was conjectured by Eric Brewer in 2000, and proved in 2002 by Seth Gilbert and Nancy Lynch. We have: C for Consistency A for Availability P for Partition-tolerance. CAP and ACID wording - the confusion summarized First, let's see the global picture. Word Databases CAP Confusion Transaction A set of operations. The word and the concept are not used. No Durable "Once a transaction completes successfully, its changes to the state survive failures." [D2] The word and the concept are not used. No Consistent Integrity constraints on the data (data types, relations, ...) For CAP, Consistency is a shortcut for "Atomic Consistency". The atomic consistency is a consistency model. More on this later. Same word, different concepts Isolation "Even though transactions execute concurrently, it appears to each Transaction, T, that others executed either before either after T". [D2] The word is not used in CAP but the word Isolation as defined in ACID is a consistency model in CAP vocabulary. Different words but same concept Atomic All changes happen or none happen. For CAP, Atomic is a consistency model, the one used in the CAP proof. Same word, dif