diff -r 854a027c80ff -r b9edc1c1538a server/python/django2/renkanmanager/models.py
--- a/server/python/django2/renkanmanager/models.py	Wed Apr 27 16:36:30 2016 +0200
+++ b/server/python/django2/renkanmanager/models.py	Tue May 03 14:32:28 2016 +0200
@@ -60,10 +60,7 @@
             initial_revision.modification_date = initial_revision.creation_date
         initial_revision.title = new_renkan_title if new_renkan_title else "Untitled Renkan"
         if new_renkan_content:
-            try:
-                new_renkan_content_dict = json.loads(new_renkan_content)
-            except ValueError:
-                raise ValidationError("Provided content to create Renkan is not a JSON-serializable")
+            new_renkan_content_dict = json.loads(new_renkan.validate_json_content(new_renkan_content))
             new_renkan_content_dict["created"] = str(initial_revision.creation_date)
             new_renkan_content_dict["updated"] = str(initial_revision.modification_date)
         else: 
@@ -82,8 +79,7 @@
         initial_revision.content = json.dumps(new_renkan_content_dict)
         initial_revision.save()
         return new_renkan
-
-
+    
 class Renkan(models.Model):
     
     renkan_guid = models.CharField(max_length=256, default=uuid.uuid4, unique=True, blank=False, null=False) # typically UUID
@@ -142,11 +138,8 @@
         else:
             revision_to_update = Revision.objects.select_for_update().get(revision_guid=self.current_revision.revision_guid)
         
-        updated_content = content if content else current_revision.content
-        try: 
-            updated_content_dict = json.loads(updated_content)
-        except ValueError:
-            raise ValidationError(message="Provided content for Renkan is not a JSON-serializable")
+        updated_content = self.validate_json_content(content) if content else current_revision.content
+        updated_content_dict = json.loads(updated_content)
         
         # If title is passed as arg to the method, update the title in the json
         if title:
@@ -166,6 +159,49 @@
         revision_to_update.last_updated_by = updator
         revision_to_update.save()
     
+    def validate_json_content(self, content):
+        """
+            Checks that the json content is valid (keys and structures), raise a ValidationError if format is wrong or value is wrong (for ids),
+            if a key is missing, autocompletes with the empty default value
+            
+            Returns the validated json string
+        """
+        try:
+            content_to_validate_dict = json.loads(content)
+        except ValueError:
+            raise ValidationError("Provided content to create Renkan is not a JSON-serializable")
+        if "id" not in content_to_validate_dict or content_to_validate_dict["id"] == "" :
+            content_to_validate_dict["id"] = str(self.renkan_guid)
+        if "title" not in content_to_validate_dict:
+            content_to_validate_dict["title"] = ""
+        if "description" not in content_to_validate_dict:
+            content_to_validate_dict["description"] = ""
+        if "created" not in content_to_validate_dict:
+            content_to_validate_dict["description"] = ""
+        if "updated" not in content_to_validate_dict:
+            content_to_validate_dict["description"] = ""
+        expected_workspace_id = str(self.workspace.workspace_guid) if self.workspace is not None else ""
+        if "space_id" not in content_to_validate_dict:
+            content_to_validate_dict["space_id"] = expected_workspace_id
+        if "nodes" not in content_to_validate_dict:
+            content_to_validate_dict["nodes"] = []
+        if "edges" not in content_to_validate_dict:
+            content_to_validate_dict["edges"] = []
+        if "views" not in content_to_validate_dict:
+            content_to_validate_dict["views"] = []
+        if "users" not in content_to_validate_dict:
+            content_to_validate_dict["users"] = []
+        
+        if type(content_to_validate_dict["nodes"]) is not list:
+            raise ValidationError("Provided content has an invalid 'nodes' key: not a list")
+        if type(content_to_validate_dict["edges"]) is not list:
+            raise ValidationError("Provided content has an invalid 'edges' key: not a list")
+        if type(content_to_validate_dict["views"]) is not list:
+            raise ValidationError("Provided content has an invalid 'views' key: not a list")
+        if type(content_to_validate_dict["users"]) is not list:
+            raise ValidationError("Provided content has an invalid 'users' key: not a list")
+        return json.dumps(content_to_validate_dict)
+        
     @transaction.atomic
     def delete(self):
         """