diff --git a/sdk/basyx/aas/model/base.py b/sdk/basyx/aas/model/base.py
index 35ccad5a..ca22d5bb 100644
--- a/sdk/basyx/aas/model/base.py
+++ b/sdk/basyx/aas/model/base.py
@@ -28,7 +28,7 @@
 BlobType = bytes
 
 # The following string aliases are constrained by the decorator functions defined in the string_constraints module,
-# wherever they are used for an instance attributes.
+# wherever they are used for an instance's attributes.
 ContentType = str  # any mimetype as in RFC2046
 Identifier = str
 LabelType = str
diff --git a/server/app/interfaces/_string_constraints.py b/server/app/interfaces/_string_constraints.py
new file mode 100644
index 00000000..65a35fe0
--- /dev/null
+++ b/server/app/interfaces/_string_constraints.py
@@ -0,0 +1,64 @@
+# Copyright (c) 2025 the Eclipse BaSyx Authors
+#
+# This program and the accompanying materials are made available under the terms of the MIT License, available in
+# the LICENSE file of this project.
+#
+# SPDX-License-Identifier: MIT
+"""
+This module implements constraint functions for the listed constrained string types.
+All types are constrained in length (min and max).
+
+.. warning::
+    This module is intended for internal use only.
+
+The following types aliased in the :mod:`~server.app.interfaces.base` module are constrained:
+
+- :class:`~server.app.interfaces.base.CodeType`
+- :class:`~server.app.interfaces.base.ShortIdType`
+- :class:`~server.app.interfaces.base.LocatorType`
+- :class:`~server.app.interfaces.base.TextType`
+- :class:`~server.app.interfaces.base.SchemeType`
+"""
+
+from typing import Callable, Type
+from basyx.aas.model._string_constraints import check, constrain_attr, _T
+
+
+def check_code_type(value: str, type_name: str = "CodeType") -> None:
+    return check(value, type_name, 1, 32)
+
+
+def check_short_id_type(value: str, type_name: str = "ShortIdType") -> None:
+    return check(value, type_name, 1, 128)
+
+
+def check_locator_type(value: str, type_name: str = "LocatorType") -> None:
+    return check(value, type_name, 1, 2048)
+
+
+def check_text_type(value: str, type_name: str = "TextType") -> None:
+    return check(value, type_name, 1, 2048)
+
+
+def check_scheme_type(value: str, type_name: str = "SchemeType") -> None:
+    return check(value, type_name, 1, 128)
+
+
+def constrain_code_type(pub_attr_name: str) -> Callable[[Type[_T]], Type[_T]]:
+    return constrain_attr(pub_attr_name, check_code_type)
+
+
+def constrain_short_id_type(pub_attr_name: str) -> Callable[[Type[_T]], Type[_T]]:
+    return constrain_attr(pub_attr_name, check_short_id_type)
+
+
+def constrain_locator_type(pub_attr_name: str) -> Callable[[Type[_T]], Type[_T]]:
+    return constrain_attr(pub_attr_name, check_locator_type)
+
+
+def constrain_text_type(pub_attr_name: str) -> Callable[[Type[_T]], Type[_T]]:
+    return constrain_attr(pub_attr_name, check_text_type)
+
+
+def constrain_scheme_type(pub_attr_name: str) -> Callable[[Type[_T]], Type[_T]]:
+    return constrain_attr(pub_attr_name, check_scheme_type)
diff --git a/server/app/interfaces/base.py b/server/app/interfaces/base.py
index 2f23b562..45d7f058 100644
--- a/server/app/interfaces/base.py
+++ b/server/app/interfaces/base.py
@@ -25,8 +25,17 @@
 from basyx.aas.adapter.json import StrictStrippedAASFromJsonDecoder, StrictAASFromJsonDecoder, AASToJsonEncoder
 from basyx.aas.adapter.xml import xml_serialization, XMLConstructables, read_aas_xml_element
 from basyx.aas.model import AbstractObjectStore
+from basyx.aas.model.datatypes import NonNegativeInteger
 from util.converters import base64url_decode
+from . import _string_constraints
 
+# The following string aliases are constrained by the decorator functions defined in the string_constraints module,
+# wherever they are used for an instances attributes.
+CodeType = str
+ShortIdType = str
+LocatorType = str
+TextType = str
+SchemeType = str
 
 T = TypeVar("T")
 
@@ -43,10 +52,11 @@ def __str__(self):
         return self.name.capitalize()
 
 
+@_string_constraints.constrain_code_type("code")
 class Message:
-    def __init__(self, code: str, text: str, message_type: MessageType = MessageType.UNDEFINED,
+    def __init__(self, code: CodeType, text: str, message_type: MessageType = MessageType.UNDEFINED,
                  timestamp: Optional[datetime.datetime] = None):
-        self.code: str = code
+        self.code: CodeType = code
         self.text: str = text
         self.message_type: MessageType = message_type
         self.timestamp: datetime.datetime = timestamp if timestamp is not None \
@@ -203,9 +213,8 @@ def _get_slice(cls, request: Request, iterator: Iterable[T]) -> Tuple[Iterator[T
         limit_str = request.args.get('limit', default="10")
         cursor_str = request.args.get('cursor', default="1")
         try:
-            limit, cursor = int(limit_str), int(cursor_str) - 1  # cursor is 1-indexed
-            if limit < 0 or cursor < 0:
-                raise ValueError
+            limit, cursor = (NonNegativeInteger(int(limit_str)),
+                             NonNegativeInteger(int(cursor_str) - 1))  # cursor is 1-indexed
         except ValueError:
             raise BadRequest("Limit can not be negative, cursor must be positive!")
         start_index = cursor
diff --git a/server/app/interfaces/repository.py b/server/app/interfaces/repository.py
index 03a3974c..713023d0 100644
--- a/server/app/interfaces/repository.py
+++ b/server/app/interfaces/repository.py
@@ -6,32 +6,6 @@
 # SPDX-License-Identifier: MIT
 """
 This module implements the "Specification of the Asset Administration Shell Part 2 Application Programming Interfaces".
-However, several features and routes are currently not supported:
-
-1. Correlation ID: Not implemented because it was deemed unnecessary for this server.
-
-2. Extent Parameter (`withBlobValue/withoutBlobValue`):
-   Not implemented due to the lack of support in JSON/XML serialization.
-
-3. Route `/shells/{aasIdentifier}/asset-information/thumbnail`: Not implemented because the specification lacks clarity.
-
-4. Serialization and Description Routes:
-   - `/serialization`
-   - `/description`
-   These routes are not implemented at this time.
-
-5. Value, Path, and PATCH Routes:
-   - All `/…/value$`, `/…/path$`, and `PATCH` routes are currently not implemented.
-
-6. Operation Invocation Routes: The following routes are not implemented because operation invocation
-   is not yet supported by the `basyx-python-sdk`:
-   - `POST /submodels/{submodelIdentifier}/submodel-elements/{idShortPath}/invoke`
-   - `POST /submodels/{submodelIdentifier}/submodel-elements/{idShortPath}/invoke/$value`
-   - `POST /submodels/{submodelIdentifier}/submodel-elements/{idShortPath}/invoke-async`
-   - `POST /submodels/{submodelIdentifier}/submodel-elements/{idShortPath}/invoke-async/$value`
-   - `GET /submodels/{submodelIdentifier}/submodel-elements/{idShortPath}/operation-status/{handleId}`
-   - `GET /submodels/{submodelIdentifier}/submodel-elements/{idShortPath}/operation-results/{handleId}`
-   - `GET /submodels/{submodelIdentifier}/submodel-elements/{idShortPath}/operation-results/{handleId}/$value`
 """
 
 import io