diff --git a/opp/core/src/main/java/PreparationNote.java b/opp/core/src/main/java/PreparationNote.java
index f36e60920788508951009047119bdf64bcbcfc5c..58ac8db18cd34776cc09a8adb7fd9cc31973067a 100644
--- a/opp/core/src/main/java/PreparationNote.java
+++ b/opp/core/src/main/java/PreparationNote.java
@@ -5,18 +5,18 @@ import java.util.Objects;
 import java.util.Objects;
 
 public class PreparationNote {
-    private String noteId;
-    private String operationId;
-    private String content;
-
+    private String noteId;      // Eindeutige Identifikation der Notiz
+    private String operationId; // ID der zugehörigen Operation
+    private String content;     // Inhalt der Notiz
 
+    // Konstruktor zur Initialisierung der Notiz-Attribute
     public PreparationNote(String noteId, String operationId, String content) {
         this.noteId = noteId;
         this.operationId = operationId;
         this.content = content;
     }
 
-
+    // Getter und Setter Methoden für die Attribute
     public String getId() {
         return noteId;
     }
@@ -41,7 +41,7 @@ public class PreparationNote {
         this.content = content;
     }
 
-
+    // toString Methode zur Darstellung der Notiz als String
     @Override
     public String toString() {
         return "PreparationNote{" +
@@ -51,7 +51,7 @@ public class PreparationNote {
                 '}';
     }
 
-
+    // equals Methode zum Vergleichen von zwei PreparationNote Objekten
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
@@ -61,7 +61,7 @@ public class PreparationNote {
                 Objects.equals(operationId, that.operationId) &&
                 Objects.equals(content, that.content);
     }
-
+    // hashCode Methode zur Berechnung des Hashcodes eines PreparationNote Objekts
     @Override
     public int hashCode() {
         return Objects.hash(noteId, operationId, content);
diff --git a/opp/core/src/main/java/PreparationNoteCommand.java b/opp/core/src/main/java/PreparationNoteCommand.java
new file mode 100644
index 0000000000000000000000000000000000000000..4581407480159030077bd461dc98811926b06ce9
--- /dev/null
+++ b/opp/core/src/main/java/PreparationNoteCommand.java
@@ -0,0 +1,27 @@
+public class PreparationNoteCommand {
+    private String operationId;
+    private String content;
+
+    // Konstruktor zur Initialisierung der Command-Attribute
+    public PreparationNoteCommand(String operationId, String content) {
+        this.operationId = operationId;
+        this.content = content;
+    }
+
+    // Getter und Setter Methoden für die Attribute
+    public String getOperationId() {
+        return operationId;
+    }
+
+    public void setOperationId(String operationId) {
+        this.operationId = operationId;
+    }
+
+    public String getContent() {
+        return content;
+    }
+
+    public void setContent(String content) {
+        this.content = content;
+    }
+}
diff --git a/opp/core/src/main/java/PreparationNoteService.java b/opp/core/src/main/java/PreparationNoteService.java
new file mode 100644
index 0000000000000000000000000000000000000000..485c834dfa8432e1a2432823773422ba9539920d
--- /dev/null
+++ b/opp/core/src/main/java/PreparationNoteService.java
@@ -0,0 +1,9 @@
+import java.util.List;
+
+public interface PreparationNoteService {
+    PreparationNote createNote(PreparationNoteCommand command);    // Methode zum Erstellen einer neuen Notiz
+    PreparationNote updateNote(String noteId, PreparationNoteCommand command); // Methode zum Aktualisieren einer Notiz
+    void deleteNote(String noteId);                     // Methode zum Löschen einer Notiz
+    PreparationNote getNoteById(String noteId);         // Methode zum Abrufen einer Notiz nach ID
+    List<PreparationNote> getNotesByOperationId(String operationId); // Methode zum Abrufen von Notizen nach Operation-ID
+}
diff --git a/opp/core/src/main/java/Room.java b/opp/core/src/main/java/Room.java
index b0b277ec6ed67309eb3b30b33d445c754f9659df..a0de6ea20f8feb336fc332d59a35536a746f478a 100644
--- a/opp/core/src/main/java/Room.java
+++ b/opp/core/src/main/java/Room.java
@@ -2,18 +2,18 @@ import java.time.Instant;
 import java.util.Objects;
 
 public class Room {
-    private String roomId;
-    private String roomName;
-    private int capacity;
+    private String roomId;  // Eindeutige Identifikation des Raum
+    private String roomName;// Name des Raums
+    private int capacity;   // Kapazität des Raums
 
-    
+    // Konstruktor zur Initialisierung der Raum-Attribute
     public Room(String RoomId, String roomName, int capacity) {
         this.roomId = roomId;
         this.roomName = RoomName;
         this.capacity = capacity;
     }
 
-    
+    // Getter und Setter Methoden für die Attribute
     public String getRoomId() {
         return RoomId;
     }
@@ -38,7 +38,7 @@ public class Room {
         this.capacity = capacity;
     }
 
-    
+    // toString Methode zur Darstellung des Raums als String
     @Override
     public String toString() {
         return "Room{" +
@@ -48,7 +48,7 @@ public class Room {
                 '}';
     }
 
-    
+    // equals Methode zum Vergleichen von zwei Room Objekten    
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
@@ -58,10 +58,10 @@ public class Room {
                 Objects.equals(roomId, room.roomId) &&
                 Objects.equals(roomName, room.roomName);
     }
-
+    // hashCode Methode zur Berechnung des Hashcodes eines Room Objekts
     @Override
     public int hashCode() {
-        return Objects.hash(id, name, capacity);
+        return Objects.hash(roomId, roomName, capacity);
     }
 }
 
diff --git a/opp/core/src/main/java/RoomCommand.java b/opp/core/src/main/java/RoomCommand.java
new file mode 100644
index 0000000000000000000000000000000000000000..64b61b069287535d1df32231d151a2cef1404809
--- /dev/null
+++ b/opp/core/src/main/java/RoomCommand.java
@@ -0,0 +1,27 @@
+public class RoomCommand {
+    private String roomName;
+    private int capacity;
+
+    // Konstruktor zur Initialisierung der Kommando-Attribute
+    public RoomCommand(String roomName, int capacity) {
+        this.roomName = roomName;
+        this.capacity = capacity;
+    }
+
+    // Getter und Setter Methoden für die Attribute
+    public String getRoomName() {
+        return roomName;
+    }
+
+    public void setRoomName(String roomName) {
+        this.roomName = roomName;
+    }
+
+    public int getCapacity() {
+        return capacity;
+    }
+
+    public void setCapacity(int capacity) {
+        this.capacity = capacity;
+    }
+}
diff --git a/opp/core/src/main/java/RoomService.java b/opp/core/src/main/java/RoomService.java
new file mode 100644
index 0000000000000000000000000000000000000000..35eb0b2002c13e28dd4d8ccd673d1503ddfa5820
--- /dev/null
+++ b/opp/core/src/main/java/RoomService.java
@@ -0,0 +1,9 @@
+import java.util.List;
+
+public interface RoomService {
+    Room createRoom(RoomCommand command);    // Methode zum Erstellen eines neuen Raums
+    Room updateRoom(String roomId, RoomCommand command); // Methode zum Aktualisieren eines Raums
+    void deleteRoom(String roomId);           // Methode zum Löschen eines Raums
+    Room getRoomById(String roomId);          // Methode zum Abrufen eines Raums nach ID
+    List<Room> getAllRooms();                 // Methode zum Abrufen aller Räume
+}
diff --git a/opp/core/target/classes/PreparationNote.class b/opp/core/target/classes/PreparationNote.class
index 72384e2f7fc261c236f087afa4319a01dc284c35..c25ee08f38b5dc6011cf268c640783d8921566e0 100644
Binary files a/opp/core/target/classes/PreparationNote.class and b/opp/core/target/classes/PreparationNote.class differ
diff --git a/opp/core/target/classes/Room.class b/opp/core/target/classes/Room.class
index b1a86260e2acc5235ce99a8ea0ce8a1e0fcd363a..fb0932d7270622d0b902788c72d0edbbdff7663f 100644
Binary files a/opp/core/target/classes/Room.class and b/opp/core/target/classes/Room.class differ