diff --git a/demos/hello_wolf/hello_wolf.cpp b/demos/hello_wolf/hello_wolf.cpp
index 3ed9d2589be2017fb8b365a0f428cfa7b0033ed2..4cc0318e2772468927932023a0dbcd8dd0090e40 100644
--- a/demos/hello_wolf/hello_wolf.cpp
+++ b/demos/hello_wolf/hello_wolf.cpp
@@ -124,14 +124,12 @@ int main()
 
     // sensor odometer 2d
     YAML::Node params_sen_odo;
-    params_sen_odo["states"]["P"]["type"]    = "StatePoint2d";
-    params_sen_odo["states"]["P"]["state"]   = Vector2d::Zero();
-    params_sen_odo["states"]["P"]["mode"]    = "fix";
-    params_sen_odo["states"]["P"]["dynamic"] = false;
-    params_sen_odo["states"]["O"]["type"]    = "StateAngle";
-    params_sen_odo["states"]["O"]["state"]   = Vector1d::Zero();
-    params_sen_odo["states"]["O"]["mode"]    = "fix";
-    params_sen_odo["states"]["O"]["dynamic"] = false;
+    params_sen_odo["states"]["P"]["value"]         = Vector2d::Zero();
+    params_sen_odo["states"]["P"]["prior"]["mode"] = "fix";
+    params_sen_odo["states"]["P"]["dynamic"]       = false;
+    params_sen_odo["states"]["O"]["value"]         = Vector1d::Zero();
+    params_sen_odo["states"]["O"]["prior"]["mode"] = "fix";
+    params_sen_odo["states"]["O"]["dynamic"]       = false;
 
     params_sen_odo["name"]           = "Sensor Odometry";
     params_sen_odo["k_disp_to_disp"] = 0.1;
@@ -163,14 +161,12 @@ int main()
 
     // sensor Range and Bearing
     YAML::Node params_sen_rb;
-    params_sen_rb["states"]["P"]["type"]    = "StatePoint2d";
-    params_sen_rb["states"]["P"]["state"]   = Vector2d::Zero();
-    params_sen_rb["states"]["P"]["mode"]    = "fix";
-    params_sen_rb["states"]["P"]["dynamic"] = false;
-    params_sen_rb["states"]["O"]["type"]    = "StateAngle";
-    params_sen_rb["states"]["O"]["state"]   = Vector1d::Zero();
-    params_sen_rb["states"]["O"]["mode"]    = "fix";
-    params_sen_rb["states"]["O"]["dynamic"] = false;
+    params_sen_rb["states"]["P"]["value"]         = Vector2d::Zero();
+    params_sen_rb["states"]["P"]["prior"]["mode"] = "fix";
+    params_sen_rb["states"]["P"]["dynamic"]       = false;
+    params_sen_rb["states"]["O"]["value"]         = Vector1d::Zero();
+    params_sen_rb["states"]["O"]["prior"]["mode"] = "fix";
+    params_sen_rb["states"]["O"]["dynamic"]       = false;
 
     params_sen_rb["name"]                      = "Sensor Range Bearing";
     params_sen_rb["noise_range_metres_std"]    = 0.1;
diff --git a/demos/hello_wolf/schema/SensorRangeBearing.schema b/demos/hello_wolf/schema/SensorRangeBearing.schema
index 72399bf82f0d97581f86134fdb95aa698a3038cf..47b551f304b23d7687ad46cc741d8fd2f1a53a5d 100644
--- a/demos/hello_wolf/schema/SensorRangeBearing.schema
+++ b/demos/hello_wolf/schema/SensorRangeBearing.schema
@@ -11,11 +11,6 @@ noise_bearing_degrees_std:
   _doc: Standard deviation of the noise of the bearing measurements (degrees)
 
 states:
-  keys:
-    _value: PO
-    _mandatory: false
-    _type: string
-    _doc: The keys corresponding to the states of the sensor.
   P:
     follow: StateSensorP2d.schema
   O: