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= Analysis =
== Overview ==
The goal of this task is to develop a scheme on how to implement a history of changes resulting from the work of the user with Sophie 2 and provide access to any given point in time in this history. [[BR]]
This way a snapshot of the state of Sophie 2 at a given time point could be obtained for various purposes such as:
 * debugging
 * reverting changes
 * feeding the change manager with needed info
 * etc.

== Task requirements ==
 * Propose ideas for the structure of the history of changes. It should be flexible enough, so the queries as the following could be answered:
  * get a snapshot of the state of all properties at a given time point
  * get the value of a given property at a given time point
  * get a history of all the values of a given property at a given time point
  * get a list of all Changes that affect a given property before and after a given time point
  * get a list of properties which a Change affects
 * Since these operations might turn out quite slow, performance should be taken into consideration as early as possible:
  * provide rough ideas on how these operations could be implemented algorithmically efficient
  * also provide ideas for suitable data structures which could improve the performance
 * Provide rough implementation of the above ideas, if possible
 * Add unit test for the implementation, if possible

== Task result ==
 * Design ideas and diagrams of the proposed solutions to the given problems in this page
 * New code and unit tests, if any

== Implementation idea ==
 * Consider using some data structure which provides logarithmic time for some of the queries
 * Try providing ideas for data structures and algorithms which perform at least some of the queries efficiently. Different approaches might be possibly combined to yield good results.

== Related ==
[wiki:PRO_LIB_CORE_TUTORIAL] [[BR]]
[wiki:PRO_CHANGE_MANAGER_R0] [[BR]]
[wiki:PRO_CHANGE_MERGING_R0] [[BR]]
[wiki:PRO_CHANGE_PRIMITIVES_R0] [[BR]]
[wiki:PRO_CHANGE_UNDO_MANAGER_R0]

== How to demo ==
 * Show this page and explain the problems and proposed solutions
 * Run the unit tests, if any

= 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.)