otly: a framework for realtime collaboration

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OTLYA framework for realtime collaborationFabio Mancinelli

fabio.mancinelli@xwiki.com

Operational Transformation is a technique for synchronizing changes to a document among different clients. It is widely used in different technologies both open and closed source (e.g., ShareJS, Apache Wave and Google Drive Realtime API) OTLY is a framework based on Operational Transformation that is being developed by XWiki SAS as a refactoring of its realtime editor. OTLY aims at providing a common foundation for contributing collaborative document models and binding to widely used editors. OTLY is targeting both Java and Javascript for the client side, and Java on the server side.

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OT Everywhere !● NodeJS based – Open Source

● ShareJS● TogetherJS ● Etherpad● ...a lot more !

● Java based – Open Source

● Apache Wave● OpenCoWeb

● Proprietary

● Google Drive Realtime API

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OTLY

● Framework targeting the Java world● Based on Operational Transformation (OT)● Embeddable in Java programs● Extensible● Simple API

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What is OT ?

● Optimistic concurrency control mechanism● Used in high-latency, low bandwidth systems● Basic blocks : operations + transformations

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What is OT ?

xform(c, s) = (c', s') | c s' = s c'∘ ∘

C S

S' C'

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What is OT ?

xform(c, s) = (c', s') | c s' = s c'∘ ∘

C S

S' C'

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What is OT ?

...

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OTLY Architecture

● Document models● For supporting different types of operations :

text, rich text, spreadsheets, etc.● Bindings

● For supporting different types of editors : HTML text area, WYSIWYG editors, etc.

● GWT for simplifying code sharing on Javascript clients and Java server

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OTLY API

● Simple API (inspired by ShareJS)● Client side (JS)

– otly = new otly.Otly() ;pad = document.getElementById("pad")otly.open("simpletext", "foo", function(doc) {

doc.bind(pad, "textarea") ;}) ;

● Client side (Java)– JFrame frame = ...

otly = new Otly() ;DocumentModel documentModel = otly.open("simpletext", "foo") ;documentModel.bind(frame) ;

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Conclusion● Extensible architecture

● Helps to build a community that provides new document models and bindings

● We are working on a reference implementation that will work with the XWiki WYSIWYG + other popular simple text editors and will be integrated in XWiki

● Issues● OT is complex to get it right● GWT is very heavyweight

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Acknowledgements

● Some of the work has been done in the context of the RESILIENCE Project

● OTLY is based on the initial work done in the context of the Wiki3.0 project by the INRIA Score Team and XWiki SAS