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= Analysis =
== Overview ==
The goal of this task is to create a concept on how to deal with online collaboration when multiple users are working on the same thing and some sort of merging their work needs to be done. [[BR]]
In Sophie 2's context, the problems which occur should be described in terms of Changes and ProLib primitives.

== Task requirements ==
 * Describe a simplified version of the general situation with online collaboration:
  * there's a server
  * there are two users of connected to this server who are working on a shared resource
  * the server holds a log of changes up to some point of time (a ''synchropoint'') and the two users are synchronized up to this point
  * each user performs his own set of changes
  * both users upload their set of changes to the server so there's a conflict

 * Some of the problems that arise are:
  * how to express each user's changeset in terms of Changes and ProLib primitives
  * how to implement merging:
   * in what order to merge the subchanges of the two users' changesets
   * how to handle operations from the different changesets which lead to invalid sequence of changes (for instance, one user inserts something in a frame, and the other user has already deleted the frame)
  * how to implement it efficiently
  * what if each user has a view on a model shared on the server and changes affecting this model are merged
   * in what extent are the two views updated?
   * some text, for instance, could be merged
   * the text cursor position shouldn't be changed though, because if you exploit this approach for everything, at the end you are left with multiple users sharing the same view
   * propose an idea how to solve this problem

 * Provide ideas for solutions for the above problems

 * Provide rough implementation of merging

== Task result ==
 * New code that meets the above requirements
 * Add appropriate tests for the code
 * Proposals for solutions to the described problems
 * Graphic explanation of the general synchronization problem described above

== Implementation idea ==
 * For the graphics, provide a graphic of both users' changesets and the log of changes on the server, viewed as lists of Changes/primitives
 * Think of different schemes how to solve the merging problem:
  * first the entire changeset of the first user is uploaded and then the changeset of the second user
  * the two changesets are merged by sorting all incoming changes by the time of their actual occurrence
  * propose other if you have any ideas

== Related ==
[wiki:PRO_CHANGE_PRIMITIVES_R0] [[BR]]
[wiki:PRO_CHANGE_UNDO_MANAGER_R0] [[BR]]
[wiki:PRO_CHANGE_TRANSACTION_SAFETY_R0] [[BR]]
[wiki:PRO_CHANGE_COMPOSING_R0] [[BR]]
[wiki:PRO_CHANGE_MANAGER_R0] [[BR]]

== How to demo ==
 * Show the new code
 * Run the tests
 * Show the explanation graphics for the general problem
 * Explain shortly the problems and discuss the proposed solutions

= Design =
^(Describe your design here.)^

= Implementation =
^(Describe and link the implementation results here (from the wiki or the repository).)^

= Testing =
^(Place the testing results here.)^

= Comments =
^(Write comments for this or later revisions here.)