diff --git a/.gradle/buildOutputCleanup/buildOutputCleanup.lock b/.gradle/buildOutputCleanup/buildOutputCleanup.lock
index 847deb8..a64b376 100644
Binary files a/.gradle/buildOutputCleanup/buildOutputCleanup.lock and b/.gradle/buildOutputCleanup/buildOutputCleanup.lock differ
diff --git a/.gradle/buildOutputCleanup/cache.properties b/.gradle/buildOutputCleanup/cache.properties
index 79b47e9..9fc555b 100644
--- a/.gradle/buildOutputCleanup/cache.properties
+++ b/.gradle/buildOutputCleanup/cache.properties
@@ -1,2 +1,2 @@
-#Wed Feb 19 20:29:41 CET 2020
-gradle.version=6.0.1
+#Thu Feb 20 16:16:13 CET 2020
+gradle.version=6.2
diff --git a/.idea/misc.xml b/.idea/misc.xml
index cf95fe9..8f27022 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_12" project-jdk-name="12.0.1" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" default="false" project-jdk-name="11" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file
diff --git a/backend.iml b/backend.iml
new file mode 100644
index 0000000..1eae0df
--- /dev/null
+++ b/backend.iml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <excludeFolder url="file://$MODULE_DIR$/.gradle" />
+      <excludeFolder url="file://$MODULE_DIR$/build" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>
\ No newline at end of file
diff --git a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java
index 12575d0..667b587 100644
--- a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java
+++ b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java
@@ -2,6 +2,8 @@ package ch.usi.inf.sa4.sanmarinoes.smarthut.models;
 
 import com.google.gson.annotations.Expose;
 
+import java.util.concurrent.atomic.AtomicLong;
+
 //Rules
 
 /**
@@ -17,7 +19,7 @@ public abstract class Device {
         OUTPUT
     }
 
-    private static long nextId = 1;
+    private static AtomicLong nextId = new AtomicLong(1);
 
     /**
      * Device identifier
@@ -49,10 +51,7 @@ public abstract class Device {
     }
 
     public Device(String kind, FlowType flowType) {
-        synchronized (Device.class) {
-            this.id = nextId;
-            nextId++;
-        }
+        this.id = nextId.getAndIncrement();
         this.kind = kind;
         this.flowType = flowType;
         this.name = kind + " " + this.id;
diff --git a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/DimmableLight.java b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/DimmableLight.java
index 988d4b5..1fb140c 100644
--- a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/DimmableLight.java
+++ b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/DimmableLight.java
@@ -14,6 +14,9 @@ public class DimmableLight extends Light implements DimmableOutput {
 
     @Override
     public void dimTo(int level) {
+        if(level<0 || level>100){
+            throw new java.lang.Error("The intensity level can't go below 0 or above 100");
+        }
         intensity = level;
     }
 }
diff --git a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Room.java b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Room.java
new file mode 100644
index 0000000..f073e43
--- /dev/null
+++ b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Room.java
@@ -0,0 +1,27 @@
+package ch.usi.inf.sa4.sanmarinoes.smarthut.models;
+import java.util.*;
+
+public class Room {
+    private ArrayList<Device> devices;
+
+    //Constructor
+    public Room(){
+        this.devices=new ArrayList<Device>();
+    }
+
+    //add a device to the list
+    public void addDevice(Device device){
+        if(!this.devices.contains(device)){
+            this.devices.add(device);
+        }
+    }
+
+    //remove a certain device from the Room
+    public void removeDevice(Device device){
+        int a=this.devices.indexOf(device);
+        if(a!=-1) {
+            this.devices.remove(a);
+        }
+    }
+
+}
diff --git a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/house.java b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/house.java
new file mode 100644
index 0000000..49c17fa
--- /dev/null
+++ b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/house.java
@@ -0,0 +1,29 @@
+package ch.usi.inf.sa4.sanmarinoes.smarthut.models;
+
+import java.util.ArrayList;
+
+public class house {
+    //a list of the rooms present in the house
+    private ArrayList<Room> rooms;
+
+    //Constructor
+    public house(){
+        this.rooms=new ArrayList<Room>();
+    }
+
+    //this method add a Room to the house
+    public void addRoom(Room room){
+        if(!this.rooms.contains(room)) {
+            this.rooms.add(room);
+        }
+    }
+
+    //this method removes the given room if it is present in the house
+    public void remove(Room room){
+        int a=this.rooms.indexOf(room);
+        if(a!=-1) {
+            this.rooms.remove(a);
+        }
+    }
+
+}