diff --git a/app/travels/webapp/index.html b/app/travels/webapp/index.html
index 98f26b6..c37cb0b 100644
--- a/app/travels/webapp/index.html
+++ b/app/travels/webapp/index.html
@@ -16,7 +16,7 @@
     </style>
     <script
       id="sap-ui-bootstrap"
-      src="https://ui5.sap.com/1.136.8/resources/sap-ui-core.js"
+      src="https://ui5.sap.com/1.136.12/resources/sap-ui-core.js"
       data-sap-ui-theme="sap_horizon"
       data-sap-ui-oninit="module:sap/ui/core/ComponentSupport"
       data-sap-ui-resourceroots='{ "sap.capire.travels": "." }'
diff --git a/db/constraints.cds b/db/constraints.cds
deleted file mode 100644
index 2d3175c..0000000
--- a/db/constraints.cds
+++ /dev/null
@@ -1,23 +0,0 @@
-using { sap.capire.travels as my } from './schema';
-
-@assert.constraint.beginAfterEnd: {
-  condition: (BeginDate <= EndDate),
-  message: 'End Date must be after Begin Date.',
-  targets: [(EndDate)]
-}
-annotate my.Travels with {
-  @mandatory BeginDate;
-  @mandatory EndDate;
-  @mandatory Agency;
-  @mandatory Customer;
-}
-
-annotate my.Bookings with {
-  @mandatory Flight;
-  @mandatory Travel;
-}
-
-annotate my.Travels with @Capabilities.FilterRestrictions.FilterExpressionRestrictions: [
-  { Property: 'BeginDate', AllowedExpressions : 'SingleRange' },
-  { Property: 'EndDate', AllowedExpressions : 'SingleRange' }
-];
diff --git a/db/schema.cds b/db/schema.cds
index e22b261..2ac8265 100644
--- a/db/schema.cds
+++ b/db/schema.cds
@@ -8,7 +8,7 @@ using {
 
 
 entity Travels : managed {
-  key ID       : Integer default 0 @readonly;
+  key ID       : Integer default 0;
   Description  : String(1024);
   BeginDate    : Date default $now;
   EndDate      : Date default $now;
diff --git a/pom.xml b/pom.xml
index 7dd167b..34f5f0d 100644
--- a/pom.xml
+++ b/pom.xml
@@ -169,4 +169,4 @@
 			</plugin>
 		</plugins>
 	</build>
-</project>
\ No newline at end of file
+</project>
diff --git a/srv/src/main/resources/messages.properties b/srv/src/main/resources/messages.properties
new file mode 100644
index 0000000..f43ae27
--- /dev/null
+++ b/srv/src/main/resources/messages.properties
@@ -0,0 +1,5 @@
+ASSERT_ENDDATE_AFTER_BEGINDATE=End date must be after begin date
+ASSERT_BOOKINGS_IN_TRAVEL_PERIOD=All bookings must be within the travel period
+ASSERT_BOOKING_CURRENCY_MATCHES_TRAVEL=All bookings must use the same currency as the travel
+ASSERT_FLIGHT_PRICE_POSITIVE=Flight price must be a positive value
+ASSERT_BOOKING_FEE_NON_NEGATIVE=Booking fee cannot be negative
diff --git a/srv/src/main/resources/messages_de.properties b/srv/src/main/resources/messages_de.properties
new file mode 100644
index 0000000..0071bfa
--- /dev/null
+++ b/srv/src/main/resources/messages_de.properties
@@ -0,0 +1,5 @@
+ASSERT_ENDDATE_AFTER_BEGINDATE=Enddatum muss nach dem Anfangsdatum liegen
+ASSERT_BOOKINGS_IN_TRAVEL_PERIOD=Alle Buchungen müssen innerhalb des Reisezeitraums liegen
+ASSERT_BOOKING_CURRENCY_MATCHES_TRAVEL=Alle Buchungen müssen dieselbe Währung wie die Reise verwenden
+ASSERT_FLIGHT_PRICE_POSITIVE=Der Flugpreis muss ein positiver Wert sein
+ASSERT_BOOKING_FEE_NON_NEGATIVE=Buchungsgebühr kann nicht negativ sein
diff --git a/srv/src/main/resources/messages_fr.properties b/srv/src/main/resources/messages_fr.properties
new file mode 100644
index 0000000..dd71aff
--- /dev/null
+++ b/srv/src/main/resources/messages_fr.properties
@@ -0,0 +1,5 @@
+ASSERT_ENDDATE_AFTER_BEGINDATE=La date de fin doit être postérieure à la date de début
+ASSERT_BOOKINGS_IN_TRAVEL_PERIOD=Toutes les réservations doivent être dans la période de voyage
+ASSERT_BOOKING_CURRENCY_MATCHES_TRAVEL=Toutes les réservations doivent utiliser la même devise que le voyage
+ASSERT_FLIGHT_PRICE_POSITIVE=Le prix du vol doit être une valeur positive
+ASSERT_BOOKING_FEE_NON_NEGATIVE=Les frais de réservation ne peuvent pas être négatifs
diff --git a/srv/src/test/java/sap/capire/xtravels/TravelServiceIntegrationTest.java b/srv/src/test/java/sap/capire/xtravels/TravelServiceIntegrationTest.java
index aca2429..6d9181f 100644
--- a/srv/src/test/java/sap/capire/xtravels/TravelServiceIntegrationTest.java
+++ b/srv/src/test/java/sap/capire/xtravels/TravelServiceIntegrationTest.java
@@ -120,9 +120,11 @@ void shouldCreateAndRetrieveTravelWithBookingsSuccessfully() throws Exception {
     booking.setFlightId("GA0322");
     booking.setFlightDate(LocalDate.of(2024, 6, 2));
     booking.setFlightPrice(BigDecimal.valueOf(1103));
+    booking.setCurrencyCode("EUR");
     Bookings.Supplements supplement = Bookings.Supplements.create();
     supplement.setBookedId("bv-0001");
     supplement.setPrice(new BigDecimal("2.30"));
+    supplement.setCurrencyCode("EUR");
     booking.setSupplements(List.of(supplement));
     travel.setBookings(List.of(booking));
 
diff --git a/srv/travel-constraints.cds b/srv/travel-constraints.cds
new file mode 100644
index 0000000..a0f97c8
--- /dev/null
+++ b/srv/travel-constraints.cds
@@ -0,0 +1,54 @@
+using { TravelService } from './travel-service';
+
+
+annotate TravelService.Travels with {
+
+  Description @assert: (case
+    when length(Description) < 3 then 'Description too short'
+  end);
+
+  Agency @assert: (case
+    when not exists Agency then 'Agency does not exist'
+  end);
+
+  Customer @assert: (case
+    when Customer is null then 'Customer must be specified'
+    when not exists Customer then 'Customer does not exist'
+  end);
+
+  EndDate @assert: (case
+    when EndDate < BeginDate then error('ASSERT_ENDDATE_AFTER_BEGINDATE', null, (BeginDate, EndDate))
+  end);
+
+  BookingFee @assert: (case
+    when BookingFee < 0 then 'ASSERT_BOOKING_FEE_NON_NEGATIVE'
+  end);
+
+};
+
+
+annotate TravelService.Bookings with {
+
+  Flight {
+    date @assert: (case
+      when date not between $self.Travel.BeginDate and $self.Travel.EndDate then 'ASSERT_BOOKINGS_IN_TRAVEL_PERIOD'
+    end);
+  }
+
+  FlightPrice @assert: (case
+    when FlightPrice < 0 then 'ASSERT_FLIGHT_PRICE_POSITIVE'
+  end);
+
+  Currency {
+    code @assert: (case
+      when code != $self.Travel.Currency.code then 'ASSERT_BOOKING_CURRENCY_MATCHES_TRAVEL'
+    end);
+  }
+
+};
+
+
+annotate TravelService.Travels with @Capabilities.FilterRestrictions.FilterExpressionRestrictions: [
+  { Property: 'BeginDate', AllowedExpressions : 'SingleRange' },
+  { Property: 'EndDate', AllowedExpressions : 'SingleRange' }
+];