Talk done by Laurent Delaigue @laurentelaigue (Obeo) + Philip Langer @PhilChip23 (EclipseSource) Dealing with comparison and merge of large models in large teams When teams work together on EMF models, they quickly face the diff/merge hell. Version control is very well addressed for code and textual files by modern VCS such as our favourite git (and its great Eclipse integration with EGit). But this does not address the issue for users collaborating on structured data, such as EMF(-based) models: For instance, try and merge model files in a textual manner, you’ll realize that your models tend to get corrupted. If you ever tried to merge XMI files, you know what I mean… So we’ve been working on EMF Compare and EGit to integrate the Eclipse Team ‘logical model’ concept to give users the capacity to efficiently compare and merge models accurately, taking the semantics into account. This enables git-based collaboration workflows to work seamlessly with models, thus preventing corruption of data during merges, rebases, and so on. In this talk, we will describe use-cases where lack of support for logical models prevents collaborative work on structured data from being effective. We will also explain how we support each use-case with EMFCompare + EGit to achieve efficient collaboration on models split in hundreds of resources with teams of tens of people located in different time-zones.

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EMF Compare ♥ EGit
Seamless Collaborative Modeling

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Laurent Delaigue
@laurentdelaigue
laurent.delaigue@obeo.fr
Philip Langer
@PhilChip23
planger@eclipsesource.com
$ whoami

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Comparing & Merging Code

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Comparing & Merging Code

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Comparing and Merging Models

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Comparing and Merging Models

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Let’s bring git to graphical modelers!
Goal
Allow teams to
work on
graphical models
in a
collaborative manner
Context
open-source

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Full-featured UML
modeler in eclipse
Generic Editor
for Graphical Syntax
Compare and merge EMF models

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JGit: Java Implementation of Git
EGit: Integration of JGit in eclipse

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XML/XMI and
Textual Merge
After all, XML files are textual files…
Why should there be a problem to
merge them?

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XML/XMI & Textual Merge - Human Factors
Users are not UML or EMF experts
Users don’t want to see XML/XMI
Users cannot be aware
of the tool’s logic and internal rules
Metamodel???
Hundreds of concepts in UML
That’s NOT what they manipulate in the editor,
why should they see that when merging?
To many users, XMI is as clear as binary
Tools hide complexity
Separation of semantics and representation

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XML/XMI & Textual Merge - Technical Factors

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XML/XMI & Textual Merge - Technical Factors

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Logical Model
Ensuring Consistency
What?
Materialize the fact that a model is
made of several (numerous) files
Why?
Keep consistency of models during
commits, merges, …

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Logical Model - Definition

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Logical Model - Definition

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Logical Model - Application

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Logical Model - Application

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Logical Model - Scope Configuration

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Logical Model - Git Interaction
Need to compare/merge all the files together
⇒ Compute the logical model for each version (Local, remote, common ancestor)

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User Stories

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Story 1
Logical Model and committing
As a user,
I want to commit all my related
changes at a time
So that I don’t corrupt my model in
any commit

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Story 2
Textual Merge
vs
Model Merge
Simple Cases
As a user,
I want to apply my local
modifications on top of the master
branch
So that I can then benefit from
master changes

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Story 3
Textual Merge
vs
Model Merge
Complex Cases
As a user
I want to compare my local work
(extracted a package in a new
project and changed the content)
with the master branch
So that I know if my work can be
merged on master

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Story 4
Conflict management
As a user,
I want to resolve conflicts between
my work and the master branch
So that I can merge my work on
master

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Perspectives
Deploy and collect feedback
Better integration with EGit
Specific build require for now…
Improve Performance
Improve Usability
Make Tool support more generic
Profiles, Other graphical notations

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Thank you!

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Useful links
http://www.eclipse.org/egit/
https://www.eclipse.org/emf/compare/
http://www.collaborative-modeling.org/
https://www.eclipse.org/papyrus/
http://www.eclipse.org/sirius/

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Credits
Mona Lisa - https://fr.wikipedia.org/wiki/La_Joconde by Leonardo da Vinci Public Domain
The Scream - https://fr.wikipedia.org/wiki/Le_Cri by Edvard Munch Public Domain
User Stories -https://www.flickr.com/photos/psd/3731275681/ cc by 2.0
https://creativecommons.org/licenses/by/2.0/
Perspectives https://unsplash.com/photos/T72-kQyQxtA by Jeffrey Swanson cc0 1.0 (Public Domain)
http://creativecommons.org/publicdomain/zero/1.0/
One last thg -https://unsplash.com/photos/RbbdzZBKRDY by Nitish Meena cc0 1.0 (Public Domain)
Useful links - https://unsplash.com/photos/FDkT3DpYBoI by Topich cc0 1.0 (Public Domain)