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diff --git a/documentation/gui.md b/documentation/gui.md
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..bcc8913fe6a20feb3d35273d3cd4dcfde7d54317 100644
--- a/documentation/gui.md
+++ b/documentation/gui.md
@@ -0,0 +1,3 @@
+# GUI description
+
+
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diff --git a/documentation/py4j.md b/documentation/py4j.md
new file mode 100644
index 0000000000000000000000000000000000000000..19bcf82b9b08de5529e3ee4f2f86fd0814728dd4
--- /dev/null
+++ b/documentation/py4j.md
@@ -0,0 +1,11 @@
+# Using Py4j
+[Py4j](https://www.py4j.org/) is a Python/Java tool allowing control java code with python.
+
+Demos are available in the [py4j_demo](py4j_demo) directory.
+
+A minimalistic main is provided at `py4j.Main.java`. Please note that py4j use socket, so only one process of that main can be executed at a given time. You can have multiple amoeba on a same process, but only one GUI on the same process. If you need to launch multiple amoebas with GUI at a same time, check py4j official documentation on how to change sockets.
+
+To compile AMOEBA as an executable jar with this main, do :
+```
+mvn clean compile assembly:single -Dmain.class=py4j.Main
+```
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diff --git a/documentation/py4j_demo/README.md b/documentation/py4j_demo/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..a4b64cc9539e079618c23c5c48df8dbd6a579809
--- /dev/null
+++ b/documentation/py4j_demo/README.md
@@ -0,0 +1,30 @@
+# Install :
+Install python dependencies :
+```
+pip3 install requirements.txt
+```
+Optional : check [openai gym](https://gym.openai.com/) documentation for a full install.
+
+Run the setup script [setup.sh](setup.sh) (linux only)
+
+You're good to go, check that py4j is correctly working with [basic_demo.py](basic_demo.py) :
+```
+python3 basic_demo.py
+```
+You should get the classic amoeba's GUI, and random context appearing.
+
+Then you can look at some actual learning, inside [learn_gym.py](learn_gym.py).
+
+
+# Optional : Ros2Learn
+[Ros2Learn](https://github.com/AcutronicRobotics/ros2learn) provide some tools for machine learning on robots, using Ros2, openAI gym, and gazebo.
+
+Install Ros2 and Ros2learn, follow Ros2Learn instruction. Make sure your version of gazebo is at least 9.9.
+
+In your python script, import gym_gazebo2. Before running your python code make sure that you properly loaded Ros2 and Ros2learn environment using their provision scripts.
+
+You can now use gym environment provided by Ros2learn as regular gym environment.
+```Python
+env = gym.make('MARA-v0')
+```
+
diff --git a/documentation/py4j_demo/learn_gym.py b/documentation/py4j_demo/learn_gym.py
index d21dcae6757358d86309c8bf21068a9c7cca1b70..ffc206c3186b3bcdc945bb21e877a2d40d82e764 100644
--- a/documentation/py4j_demo/learn_gym.py
+++ b/documentation/py4j_demo/learn_gym.py
@@ -1,6 +1,6 @@
import os
import gym
-import gym_gazebo2
+#import gym_gazebo2
import subprocess
import time
import math
diff --git a/documentation/save_system.md b/documentation/save_system.md
new file mode 100644
index 0000000000000000000000000000000000000000..4219c489f00ceb30e162ed33cdf81f37300279d7
--- /dev/null
+++ b/documentation/save_system.md
@@ -0,0 +1,54 @@
+#The Save System
+The save system is composed of two main elements, and some GUI elements :
+
+## The Backup System :
+Found in `kernel.backup`.
+
+A backup system is an object responsible for reading/writing the state of amoeba from/to a file. It implement the interface `IBackupSystem`. The implementation provided is `BackupSystem` and use xml to store data.
+
+Usage :
+```Java
+AMOEBA amoeba = new AMOEBA()
+IBackupSystem backupSystem = new BackupSystem(amoeba);
+backupSystem.load(new File("path/to/a/save.xml"));
+// do some learning with the amoeba ...
+backupSystem.save(new File("path/to/a/new/file.xml"))
+```
+
+## The Save Helper :
+Found in `kernel.backup`.
+
+A save helper is an object that provide additional functionality over a BackupSystem for the user or other components. Most importantly it :
+- Create a temporary directory for saves
+- Allow automatic saving during amoeba execution
+- Add the options to save/load on the GUI
+- Add functionality used by the SaveExplorer.
+
+See `ISaveHelper` for more.
+
+Two implementation are provided : the fully functioning `SaveHelperImpl` and `SaveHelperDummy` that do nothing. The dummy is used to deactivate ALL automatic saving, giving a HUGE performance boost.
+
+Each amoeba has a save helper, available with `amoeba.saver`
+```Java
+AMOEBA amoeba = new AMOEBA();
+// This constructor initialize the amoeba's saver with a dummy, meaning :
+amoeba.saver.save("this_does_not_save");
+// will do nothing
+
+// or ...
+AMOEBA amoeba = new AMOEBA("path/to/save.xml", null);
+// This constructor create and use a SaveHelperImpl to initilize the amoeba
+amoeba.saver.save("a/valid/path/save.xml");
+// will create a save, and
+amoeba.saver.autosave();
+// will create a save in the temporary directory creates by the save helper, located in
+System.out.println(SaveHelperImpl.dir)
+```
+If amoeba crash, the save files will not be automatically deleted, you may have to manually clean the save directory.
+
+## The Save Explorer
+Found in `gui.saveExplorer`.
+
+The save explorer read saves from an amoeba's SaveHelper and offer some graphical tool, most importantly the ability to preview a save and quickly cycle trough saves. Allowing to visually play back the execution of an amoeba.
+
+See the [GUI description](gui.md) for more detail on the GUI.
diff --git a/documentation/usage.md b/documentation/usage.md
index 352759c9a5788a13213e84dabdc1dcac627f1b07..b7235148d0d75d1ce59ae9429eb6fd0dcb84c012 100644
--- a/documentation/usage.md
+++ b/documentation/usage.md
@@ -16,7 +16,7 @@ Depending on your problem, determine what AMOEBA should learn, and from what. Bu
A config file is a xml file used to initialize your amoeba. Most importantly it contain the list of percepts.
You can use `utils/genFiles.py` to generate your xml file based on a list of percept. `python genFiles.py MySystem false px py` will create `MySystem.xml` (and `MySystem.msg`, but ignore it if you don't use [AMOEBA and ROS](rosbridge.md)) containing something looking like the following example :
-
+(if you don't want to use python, a java class doing the same job is available at `utils.XmlConfigGenerator`)
```xml
<?xml version="1.0" encoding="UTF-8"?>
<System>
@@ -144,6 +144,6 @@ public static void main(String[] args) {
}
}
```
-We can ask amoeba how well it performed on the last prediction with `amoeba.getHeads().get(0).getCriticity()`.
+We can ask amoeba how well it performed on the last prediction with `amoeba.getHeadAgent().getCriticity()`.
For more example on how to use amoeba, check `AdvancedMain.java`, `MinimalMain.java`, and `Main.java` in the `experiments` package.
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