diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3a0d6cc5339fc1db13358a02e0f80be17ccef848..627ee4e4e96626a9228a0bf319c9d1725f7e31b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   h5py is now an optional dependency
 - table importer implementations for csv and tsv
 - string-in-list check for table imports
+- Documentation and test for the `extern` keyword used by the YAML interface
 
 ### Changed ###
 
diff --git a/integrationtests/insert_model.py b/integrationtests/insert_model.py
index ae3dd7701b44f5008bd976d81f8ecc8d9a02bf89..d793b041549812aa00a030d5c7a456f45da66b09 100755
--- a/integrationtests/insert_model.py
+++ b/integrationtests/insert_model.py
@@ -5,6 +5,10 @@ from caosadvancedtools.cfoods.h5 import H5CFood
 from caosadvancedtools.models.data_model import DataModel
 from caosadvancedtools.models.parser import parse_model_from_yaml
 
+# for teseting existing data model parts for the YANL Interface
+db.RecordType(name="TestRT1", datatype=db.TEXT).insert()
+db.Property(name="TestP1", datatype=db.TEXT).insert()
+
 model = parse_model_from_yaml("model.yml")
 model.sync_data_model(noquestion=True)
 
diff --git a/integrationtests/model.yml b/integrationtests/model.yml
index e1753a9f84d6eff7a9a59c5d17ca4f9f9da7c4c6..cad7958803edf1a01f0649353443ffab350cc5e5 100644
--- a/integrationtests/model.yml
+++ b/integrationtests/model.yml
@@ -69,3 +69,6 @@ Report:
   - Publication
 hdf5File:
   datatype: REFERENCE
+extern:
+  - TestRT1
+  - TestP1
diff --git a/src/doc/yaml_interface.rst b/src/doc/yaml_interface.rst
index 06248f2b5c17f40b6f15f5f55664c5a4a5530a86..dcf4c5d6c7a674bd8d32d92df0a509e511af26f5 100644
--- a/src/doc/yaml_interface.rst
+++ b/src/doc/yaml_interface.rst
@@ -39,6 +39,9 @@ Let's start with an example taken from https://gitlab.indiscale.com/caosdb/src/c
           table:
              datatype: FILE
              description: 'A table document associated with this recording'
+    extern:
+       - Textfile
+
 
 
 This example defines 3 ``RecordType``s:
@@ -46,6 +49,9 @@ This example defines 3 ``RecordType``s:
 - A ``Project`` with one obligatory property ``datatype``
 - A Person with a ``firstName`` and a ``lastName`` (as recommended properties)
 - A ``LabbookEntry`` with multiple recommended properties of different data types
+- It is assumed that the server knows a RecordType or Property with the name 
+  "Textfile".
+
 
 One major advantage of using this interface (in contrast to the standard python interface) is that properties can be defined and added to record types "on-the-fly". E.g. the three lines for ``firstName`` as sub entries of ``Person`` have two effects on CaosDB:
 
@@ -60,6 +66,8 @@ Note the difference between the three property declarations of ``LabbookEntry``:
 - ``responsible``: This defines and adds a property with name "responsible" to ``LabbookEntry`, which has a datatype ``Person``. ``Person`` is defined above.
 - ``firstName``: This defines and adds a property with the standard data type ``TEXT`` to record type ``Person``.
 
+If the data model depends on already existing parts, those can be added using the ``extern`` keyword.
+
 Datatypes
 ---------