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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.– <INDEX, TYPE, CHAR, CID, VECTOR-TIMESTAMP>
ex: document is shared by three clients
CLIENT-1 INSERTS ABC
•<1,i , ‘A’, 1, (1,0,0)>•<2,i , ‘B’, 1, (2,0,0)>•<3,i , ‘C’, 1, (3,0,0)>
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 COMPONENTSSERVER
CLIENTClient maintains client-Id, local cache, History Buffer, site’s vector timestamp.
NEW DOCUMENTCREATE + 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. 1998. 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, 59-68. DOI=10.1145/289444.289469 http://doi.acm.org/10.1145/289444.289469
• Chengzheng Sun, Xiaohua Jia, Yanchun Zhang, Yun Yang, and David Chen. 1998. Achieving convergence, causality preservation, and intention preservation in real-time cooperative editing systems. ACM Trans. Comput.-Hum. Interact. 5, 1 (March 1998), 63-108. DOI=10.1145/274444.274447 http://doi.acm.org/10.1145/274444.274447
Thank you!!By
Ambika BabujiMalinipriya Goppannan Ravi
For COMP 512