Presentation by Chengzheng Sun and Clarence (Skip) Ellis. Real-time CE (Cooperative Editing) systems allow multiple geographically dispersed users to view and edit a shared document at the same time. The Sun and Ellis presentation discusses the Major technological components of an Operational transformation System for CE, including: Distributed computing (Computer networks/Internet), Interactive computing (Human-Computer interaction), and, Collaborative computing (Human-Human interaction). Google established Operational Transformation as the heart and soul of the Collaborative Computing Age when they used the Operational Transformation as the Wave/Federation protocol. Florian Reuter pushed OT technology further when he developed OTXML, a flowing but very rich and complex document model for Collaborative Computing.

1. Operational Transformation in Real-Time Group Editors : Issues, Algorithms, and Achievements Chengzheng Sun Charence (Skip) Ellis School of Computing and IT Dept. of Computer Science Griffith University University of Colorado Brisbane, Queensland 4111 Boulder, CO 80309-0430 Australia United States C.Sun@cit.gu.edu.au [email_address] http://www.cit.gu.edu.au/~scz http://www.cs.colorado.edu/~skip/Home.html

10. The dOPT puzzle: O2 || (O3  O1) O2 O2 is context-equivalent to O 3 O1 is context-deferent from O 2 O1 O3 Site 3 Site 1 Site 2 O1’ O1 [ O2, O3’ ] Log dOPT T At site 2 No At site 3 and 1 O2’ O2 [ O3, O1] Log dOPT T T Yes

11. The Jupiter approach Nichols et al (Xerox PARC, UIST95) Server Star-like communication topology (0, 0) (2, 0) (0, 1) (1, 0) (2, 2) (2, 1) (0, 2) (1, 1) (1, 2) server client Initial state 2-dimentional state space

12. The dOPT puzzle in another form O2 || (O3  O1) O1 O3 O2 client server O1 O3

13. Jupiter solution to the puzzle (0, 0) (2, 0) (0, 1) (1, 0) server client Initial state 2-dimentional state space O1 O3 O2 client server O3 O2 O1 (2, 1) O2’’ O1’ O2’ (1, 1) O3’

14. The adOPTed approach Ressel et al (U. of Stuttgart, CSCW96) Transformation Property 2: T(T(O, Ob), Oa’) = T(T(O, Oa), Ob’) Transformation Property 1: Oa  Ob’  Ob o Oa’ O a Ob’=T(Ob,Oa) O O b Oa’=T(Oa,Ob) N -dimentional Interaction Model S0 S1 S2 Oa Ob T(O,Ob) T(Ob,O) T(O,Oa) T(Oa,O) Ob’=T(Ob,Oa) Oa’=T(Oa, Ob) S3

15. adOPTed solution to the puzzle O2 O1 O 2 O3 Path taken by site 3 and 1 Path taken by site 2 Site 3 Site 1 Site 2 O1 O3 O2’’=T(O2’, O1) O1’=T(O1, O2’) O3’=T(O3, O2) O2’=T(O2, O3)

17. REDUCE solution to the puzzle O2 O2 || (O3  O1) O1 [ O2, O3’ ] O1’ HB GOT + + O1 O3 O3 _ _

18. An optimized algorithm: GOTO Sun and Ellis (CSCW98) O1 [ O2, O3’ ] O1’ HB GOTO O2 O1 O3 + [ O3, O2’ ] _ transpose +

25. The End