diff --git a/database-model.ts b/database-model.ts
new file mode 100644
index 0000000..d91c67d
--- /dev/null
+++ b/database-model.ts
@@ -0,0 +1,78 @@
+//
+// Prelude
+//
+
+type Natural = number
+type Integer = number
+type Rational = [number, number]
+type Real = number
+
+type Datetime = string
+type Time = string
+
+type Maybe<T> = { present: false } | { present: true; value: T }
+
+//
+// PostiDM
+//
+
+type UserPermission = 'basic' | 'helper' | 'moderator' | 'admin'
+
+type PostiDM = {
+    users: Map<UserID, User>
+    rooms: Map<RoomID, Room>
+    seats: Map<SeatID, Seat>
+    slots: Map<SlotID, Slot>
+}
+
+type UserID = string
+type User = {
+    id: UserID
+    permissions: Set<UserPermission>
+    bookings: Booking[]
+}
+
+type BookingID = string
+type Booking = {
+    id: BookingID
+    timestamp: Datetime
+    slotID: SlotID
+}
+
+type SlotID = string
+type Slot = {
+    id: SlotID
+    seatID: SeatID
+    range: {
+        from: Datetime
+        to: Datetime
+    }
+}
+
+type SeatID = string
+type Seat = {
+    id: SeatID
+    roomID: RoomID
+    diagram: {
+        x: Natural
+        y: Natural
+        width: Natural
+        height: Natural
+    }
+
+    // non mi piace questo nome
+    getCurrentOccupant(): Maybe<UserID>
+}
+
+type RoomID = string
+type Room = {
+    id: RoomID
+    seatIDs: SeatID[]
+    diagram: {
+        gridRows: Natural
+        gridCols: Natural
+    }
+
+    getTotalSeatCount(): Natural
+    getOccupiedSeatCount(): Natural
+}