COLLABORATIVE TEXT EDITOR Multiple users distributed geographically can access the same document simultaneously. CHARACTERISTICS – high concurrency – hidden latency – consistency

SCOPE EDITOR – distributed – 1D text only editor OPERATIONS – character-wise operation – insert a character – update delete at index i insert at index i

SCOPE Can be shared between any number of users. Achieves convergence – Temporary divergence is acceptable. Preserves causality of operations

CHALLENGES NO GLOBAL TIME – Distributed users. LATENCY – Latency is never zero. DIVERGENCE – Text at multiple site should converge.

SOLUTION LATENCY – document is replicated – each client/site gets a copy – PROBLEM consistency issues all the documents should converge to the same state. NO GLOBAL TIME – vector timestamps

TERMINOLOGY OPERATION – every action by user. – ex: document is shared by three clients CLIENT-1 INSERTS ABC

TERMINOLOGY

DIVERGENCE initially documents are identical executing independent operations causes the replicas to diverge

OPERATIONAL TRANSFORMATION Applying remote operations directly makes the document inconsistent Operational Transformation (OT) – guarantees convergence.

Initially documents are identical. Transform remote operations to ensure convergence of documents.

ARCHITECTURE

ENTITIES

SERVER/CLIENT COMPONENTS SERVER CLIENT Client maintains client-Id, local cache, History Buffer, site’s vector timestamp.

NEW DOCUMENT CREATE + RETRIEVE

SYNC

TECHNOLOGY STACK FRONT END – HTML, CSS, JAVASCRIPT – BOOTSTRAP, jQuery, CODE MIRROR BACK END – JAVA – JERSEY FRAMEWORK COMMUNICATION – JSON

DEMO

REFERENCES Chengzheng Sun and Clarence Ellis Operational transformation in real-time group editors: issues, algorithms, and achievements. In Proceedings of the 1998 ACM conference on Computer supported cooperative work (CSCW '98). ACM, New York, NY, USA, DOI= / Chengzheng Sun, Xiaohua Jia, Yanchun Zhang, Yun Yang, and David Chen Achieving convergence, causality preservation, and intention preservation in real-time cooperative editing systems. ACM Trans. Comput.-Hum. Interact. 5, 1 (March 1998), DOI= /