Designing a commutative replicated data type for cooperative editing systems (original) (raw)

A commutative replicated data type for cooperative editing

2009

Abstract A commutative replicated data type (CRDT) is one where all concurrent operations commute. The replicas of a CRDT converge automatically, without complex concurrency control. This paper describes Treedoc, a novel CRDT design for cooperative text editing. An essential property is that the identifiers of Treedoc atoms are selected from a dense space. We discuss practical alternatives for implementing the identifier space based on an extended binary tree.

Strong Eventual Consistency of the Collaborative Editing Framework WOOT

Arch. Formal Proofs, 2020

Commutative Replicated Data Types (CRDTs) are a promising new class of data structures for large-scale shared mutable content in applications that only require eventual consistency. The WithOut Operational Transforms (WOOT) framework is a CRDT for collaborative text editing introduced by Oster et al. (CSCW 2006) for which the eventual consistency property was verified only for a bounded model to date. We contribute a formal proof for WOOTs strong eventual consistency.

Replicated abstract data types: Building blocks for collaborative applications

Journal of Parallel and Distributed Computing, 2011

For distributed applications requiring collaboration, responsive and transparent interactivity is highly desired. Though such interactivity can be achieved with optimistic replication, maintaining replica consistency is difficult. To support efficient implementations of collaborative applications, this paper extends a few representative abstract data types (ADTs), such as arrays, hash tables, and growable arrays (or linked lists), into replicated abstract data types (RADTs). In RADTs, a shared ADT is replicated and modified with optimistic operations. Operation commutativity and precedence transitivity are two principles enabling RADTs to maintain consistency despite different execution orders. Especially, replicated growable arrays (RGAs) support insertion/deletion/update operations. Over previous approaches to the optimistic insertion and deletion, RGAs show significant improvement in performance, scalability, and reliability.

Controlled conflict resolution for replicated document

Proceedings of the 8th IEEE International Conference on Collaborative Computing: Networking, Applications and Worksharing, 2012

Collaborative working is increasingly popular, but it presents challenges due to the need for high responsiveness and disconnected work support. To address these challenges the data is optimistically replicated at the edges of the network, i.e. personal computers or mobile devices. This replication requires a merge mechanism that preserves the consistency and structure of the shared data subject to concurrent modifications.

Concurrency Effects Over Variable-size Identifiers in Distributed Collaborative Editing

2013

Distributed collaborative editors such as Google Docs or Etherpad allow to distribute the work across time, space and organizations. In this paper, we focus on distributed collaborative editors based on the Conflict-free Replicated Data Type approach (CRDT). CRDTs encompass a set of well-known data types such as sets, graphs, sequences, etc. CRDTs for sequences model a document as a set of elements (character, line, paragraph, etc.) with unique identifiers, providing two commutative update operations: insert and delete. The identifiers of elements can be either of fixed-size or variable-size. Recently, a strategy for assigning variable-size identifiers called LSEQ has been proposed for CRDTs for sequences. LSEQ lowers the space complexity of variable-size identifiers CRDTs from linear to sub-linear. While experiments show that it works locally, it fails to provide this bound with multiple users and latency. In this paper, we propose h-LSEQ, an improvement of LSEQ that preserves its ...

Scalable XML Collaborative Editing with Undo

Lecture Notes in Computer Science, 2010

Commutative Replicated Data-Type (CRDT) is a new class of algorithms that ensure scalable consistency of replicated data. It has been successfully applied to collaborative editing of texts without complex concurrency control.

A comprehensive study of convergent and commutative replicated data types

2011

Abstract: Eventual consistency aims to ensure that replicas of some mutable shared object converge without foreground synchronisation. Previous approaches to eventual consistency are ad-hoc and error-prone. We study a principled approach: to base the design of shared data types on some simple formal conditions that are sufficient to guarantee eventual consistency. We call these types Convergent or Commutative Replicated Data Types (CRDTs).

Evaluating CRDTs for real-time document editing

Proceedings of the 11th ACM symposium on Document engineering - DocEng '11, 2011

Nowadays, real-time editing systems are catching on. Tools such as Etherpad or Google Docs enable multiple authors at dispersed locations to collaboratively write shared documents. In such systems, a replication mechanism is required to ensure consistency when merging concurrent changes performed on the same document. Current editing systems make use of operational transformation (OT), a traditional replication mechanism for concurrent document editing.

Designing a commutative replicated data type

2007

Abstract: Commuting operations greatly simplify consistency in distributed systems. This paper focuses on designing for commutativity, a topic neglected previously. We show that the replicas of\ emph {any} data type for which concurrent operations commute converges to a correct value, under some simple and standard assumptions. We also show that such a data type supports transactions with very low cost. We identify a number of approaches and techniques to ensure commutativity.

Conflict-free replicated data types

2011

Replicating data under Eventual Consistency (EC) allows any replica to accept updates without remote synchronisation. This ensures performance and scalability in large-scale distributed systems (eg, clouds). However, published EC approaches are ad-hoc and error-prone. Under a formal Strong Eventual Consistency (SEC) model, we study sufficient conditions for convergence. A data type that satisfies these conditions is called a Conflict-free Replicated Data Type (CRDT).