diff --git a/bookstore/srv/mashup.cds b/bookstore/srv/mashup.cds
index 74b8f4cb..857091a6 100644
--- a/bookstore/srv/mashup.cds
+++ b/bookstore/srv/mashup.cds
@@ -10,12 +10,22 @@
 //
 using { sap.capire.bookshop.Books } from '@capire/bookshop';
 using { ReviewsService.Reviews } from '@capire/reviews';
+using { managed, cuid } from '@sap/cds/common';
+
 extend Books with {
   reviews : Composition of many Reviews on reviews.subject = $self.ID;
   rating  : type of Reviews:rating; // average rating
   numberOfReviews : Integer @title : '{i18n>NumberOfReviews}';
+  Y_characteristics : Composition of many Y_Characteristic on Y_characteristics.parent = $self;
 }
 
+entity Y_Characteristic : cuid, managed {
+  parent      : Association to one Books;
+  characteristicId : String;
+  name  : String;
+  value : String;
+  uom : String;
+}
 
 //
 //  Extend Orders with Books as Products
diff --git a/bookstore/test/requests.http b/bookstore/test/requests.http
index c42b4bd4..65080cc7 100644
--- a/bookstore/test/requests.http
+++ b/bookstore/test/requests.http
@@ -79,3 +79,36 @@ Authorization: Basic alice:
   "dateOfBirth": "1564-04-26",
   "dateOfDeath": "1616-04-23"
 }
+
+### Create book
+POST {{bookshop}}/admin/Books
+Content-Type: application/json
+Authorization: Basic alice:
+
+{
+  "ID": 291,
+  "title": "Ttile1",
+  "author_ID": 107,
+  "numberOfReviews": 3,
+  "Y_characteristics": [{
+    "ID": "e326afd9-4688-4bf5-9664-783ff997cdf5",
+    "characteristicId": "myid",
+    "name": "myname"
+  }]
+}
+
+### Update book
+PUT {{bookshop}}/admin/Books(291)
+Content-Type: application/json
+Authorization: Basic alice:
+
+{
+  "title": "Ttile111111111",
+  "author_ID": 107,
+  "numberOfReviews": 4,
+  "Y_characteristics": [{
+    "ID": "e326afd9-4688-4bf5-9664-783ff997cdf5",
+    "characteristicId": "myid123",
+    "name": "myname123"
+  }]
+}