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

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

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

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

6. 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

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

8. TERMINOLOGY

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

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

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

12. ARCHITECTURE

13. ENTITIES

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

15. NEW DOCUMENT CREATE + RETRIEVE

16. SYNC

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

18. DEMO

19. 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 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 http://doi.acm.org/10.1145/274444.274447