diff --git a/misc/sampledata.json b/misc/sampledata.json
index abe7e82..56ef685 100644
--- a/misc/sampledata.json
+++ b/misc/sampledata.json
@@ -31,28 +31,28 @@
 	"members": [
 		{
 			"id": 1,
-			"name": "Alexandra Ahorn",
-			"email_address_private": "alex-rockt@example.org",
+			"name": "alexandra",
+			"email_address": "alex-rockt@example.org",
 			"groups": [1, 2, 3]
 		},
 		{
 			"id": 2,
-			"name": "Berthold Buche",
-			"email_address_private": "bert-ohne-ernie@example.org",
+			"name": "berthold",
+			"email_address": "bert-ohne-ernie@example.org",
 			"groups": [4, 5, 2]
 		},
 		{
 			"id": 3,
-			"name": "Charlotte Castania",
-			"email_adress_private": "charly-the-unicorn@example.org",
+			"name": "charlotte",
+			"email_address": "charly-the-unicorn@example.org",
 			"groups": [4, 1]
 		}
 	],
-	"invites": [
+	"invitations": [
 		{
 			"id": 1,
 			"name_changeable": true,
-			"name_value": "Daniel Distel",
+			"name_value": "daniel",
 			"email_address_changeable": true,
 			"email_address_value": "duesentrieb@example.org",
 			"groups_changeable": false,
diff --git a/source/api/actions/group_add.ts b/source/api/actions/group_add.ts
new file mode 100644
index 0000000..c9bd86c
--- /dev/null
+++ b/source/api/actions/group_add.ts
@@ -0,0 +1,69 @@
+/*
+Espe | Ein schlichtes Werkzeug zur Mitglieder-Verwaltung | Backend
+Copyright (C) 2024 Christian Fraß
+
+This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public 
+License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later 
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied 
+warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with this program. If not, see 
+<https://www.gnu.org/licenses/>. 
+ */
+
+namespace _espe.api
+{
+	
+	/**
+	 */
+	export function register_group_add(
+		rest_subject : lib_plankton.rest_http.type_rest
+	) : void
+	{
+		lib_plankton.rest_http.register<
+			string,
+			(string | _espe.type.group_id)
+		>(
+			rest_subject,
+			lib_plankton.http.enum_method.post,
+			_espe.api.full_path("/group/add"),
+			{
+				/**
+				 * @todo translation
+				 */
+				"description": () => "erstellt eine Gruppe",
+				"input_schema": () => ({
+					"nullable": false,
+					"type": "string",
+				}),
+				"output_schema": () => ({
+					"nullable": false,
+					"type": "number",
+				}),
+				"restriction": () => restriction_logged_in,
+				"execution": () => async ({"input": input}) => {
+					if (input === null) {
+						return Promise.resolve({
+							"status_code": 400,
+							"data": ""
+						});
+					}
+					else {
+						const data = await _espe.service.group.add(
+							{
+								"name": input
+							}
+						);
+						return Promise.resolve({
+							"status_code": 200,
+							"data": data
+						});
+					}
+				}
+			}
+		);
+	}
+	
+}
diff --git a/source/api/actions/group_list.ts b/source/api/actions/group_list.ts
new file mode 100644
index 0000000..ff9ee23
--- /dev/null
+++ b/source/api/actions/group_list.ts
@@ -0,0 +1,75 @@
+/*
+Espe | Ein schlichtes Werkzeug zur Mitglieder-Verwaltung | Backend
+Copyright (C) 2024 Christian Fraß
+
+This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public 
+License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later 
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied 
+warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with this program. If not, see 
+<https://www.gnu.org/licenses/>. 
+ */
+
+namespace _espe.api
+{
+	
+	/**
+	 */
+	export function register_group_list(
+		rest_subject : lib_plankton.rest_http.type_rest
+	) : void
+	{
+		lib_plankton.rest_http.register<
+			null,
+			Array<
+				{
+					id : _espe.type.invitation_id;
+					name : string;
+				}
+			>
+		>(
+			rest_subject,
+			lib_plankton.http.enum_method.get,
+			_espe.api.full_path("/group/list"),
+			{
+				/**
+				 * @todo translation
+				 */
+				"description": () => "listet alle Gruppen auf",
+				"output_schema": () => ({
+					"type": "object",
+					"nullable": false,
+					"additionalProperties": false,
+					"properties": {
+						"id": {
+							"nullable": false,
+							"type": "intiger",
+							"description": "ID"
+						},
+						"name": {
+							"nullable": false,
+							"type": "string",
+							"description": "Name"
+						},
+					},
+					"required": [
+						"id",
+						"name",
+					]
+				}),
+				"restriction": () => restriction_logged_in,
+				"execution": () => async ({}) => {
+					const data = await _espe.service.group.list();
+					return Promise.resolve({
+						"status_code": 200,
+						"data": data
+					});
+				}
+			}
+		);
+	}
+	
+}
diff --git a/source/api/actions/group_modify.ts b/source/api/actions/group_modify.ts
new file mode 100644
index 0000000..450b135
--- /dev/null
+++ b/source/api/actions/group_modify.ts
@@ -0,0 +1,83 @@
+/*
+Espe | Ein schlichtes Werkzeug zur Mitglieder-Verwaltung | Backend
+Copyright (C) 2024 Christian Fraß
+
+This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public 
+License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later 
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied 
+warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with this program. If not, see 
+<https://www.gnu.org/licenses/>. 
+ */
+
+namespace _espe.api
+{
+	
+	/**
+	 */
+	export function register_group_modify(
+		rest_subject : lib_plankton.rest_http.type_rest
+	) : void
+	{
+		lib_plankton.rest_http.register<
+			{
+				name : string;
+			},
+			null
+		>(
+			rest_subject,
+			lib_plankton.http.enum_method.patch,
+			_espe.api.full_path("/group/modify/:id"),
+			{
+				/**
+				 * @todo translation
+				 */
+				"description": () => "ändert eine Gruppe",
+				"input_schema": () => ({
+					"nullable": false,
+					"type": "object",
+					"properties": {
+						"name": {
+							"nullable": false,
+							"type": "string",
+						}
+					},
+					"additionalProperties": false,
+					"required": [
+						"name",
+					]
+				}),
+				"output_schema": () => ({
+					"nullable": true,
+				}),
+				"restriction": () => restriction_logged_in,
+				"execution": () => async ({"path_parameters": path_parameters, "input": input}) => {
+					if (input === null) {
+						return Promise.resolve({
+							"status_code": 400,
+							"data": null
+						});
+					}
+					else {
+						const group_id : _espe.type.group_id = parseInt(path_parameters["id"]);
+						const group_object : _espe.type.group_object = {
+							"name": input.name,
+						};
+						const data = await _espe.service.group.modify(
+							group_id,
+							group_object
+						);
+						return Promise.resolve({
+							"status_code": 200,
+							"data": null
+						});
+					}
+				}
+			}
+		);
+	}
+	
+}
diff --git a/source/api/actions/group_read.ts b/source/api/actions/group_read.ts
new file mode 100644
index 0000000..4e9edbf
--- /dev/null
+++ b/source/api/actions/group_read.ts
@@ -0,0 +1,66 @@
+/*
+Espe | Ein schlichtes Werkzeug zur Mitglieder-Verwaltung | Backend
+Copyright (C) 2024 Christian Fraß
+
+This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public 
+License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later 
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied 
+warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with this program. If not, see 
+<https://www.gnu.org/licenses/>. 
+ */
+
+namespace _espe.api
+{
+	
+	/**
+	 */
+	export function register_group_read(
+		rest_subject : lib_plankton.rest_http.type_rest
+	) : void
+	{
+		lib_plankton.rest_http.register<
+			null,
+			{
+				name : string;
+			}
+		>(
+			rest_subject,
+			lib_plankton.http.enum_method.get,
+			_espe.api.full_path("/group/read/:id"),
+			{
+				/**
+				 * @todo translation
+				 */
+				"description": () => "gibt die Daten zu einer Gruppen aus",
+				"output_schema": () => ({
+					"nullable": false,
+					"type": "object",
+					"properties": {
+						"name": {
+							"nullable": false,
+							"type": "string",
+						}
+					},
+					"additionalProperties": false,
+					"required": [
+						"name",
+					]
+				}),
+				"restriction": () => restriction_logged_in,
+				"execution": () => async ({"path_parameters": path_parameters}) => {
+					const group_id : _espe.type.group_id = parseInt(path_parameters["id"]);
+					const group_object : _espe.type.group_object = await _espe.service.group.get(group_id);
+					return Promise.resolve({
+						"status_code": 200,
+						"data": group_object
+					});
+				}
+			}
+		);
+	}
+	
+}
diff --git a/source/api/functions.ts b/source/api/functions.ts
index 5e465ee..3b910fc 100644
--- a/source/api/functions.ts
+++ b/source/api/functions.ts
@@ -43,6 +43,13 @@ namespace _espe.api
 			_espe.api.register_session_begin(rest_subject);
 			_espe.api.register_session_end(rest_subject);
 		}
+		// group
+		{
+			_espe.api.register_group_list(rest_subject);
+			_espe.api.register_group_read(rest_subject);
+			_espe.api.register_group_add(rest_subject);
+			_espe.api.register_group_modify(rest_subject);
+		}
 		// member
 		{
 			_espe.api.register_member_summon(rest_subject);
diff --git a/source/repositories/group.ts b/source/repositories/group.ts
index 9129ba7..c4c4ace 100644
--- a/source/repositories/group.ts
+++ b/source/repositories/group.ts
@@ -84,7 +84,7 @@ namespace _espe.repository.group
 	) : _espe.type.group_object
 	{
 		return {
-			"name": dispersal.core_row["name"],
+			"name": dispersal["name"],
 		};
 	}
 	
@@ -98,9 +98,7 @@ namespace _espe.repository.group
 		Array<
 			{
 				id : _espe.type.group_id;
-				preview : {
-					name : string;
-				};
+				name : string;
 			}
 		>
 	>
@@ -123,9 +121,7 @@ namespace _espe.repository.group
 			.map(
 				({"key": key, "preview": preview}) => ({
 					"id": key,
-					"preview": {
-						"name": preview["name"],
-					}
+					"name": preview["name"],
 				})
 			)
 		);
@@ -138,11 +134,9 @@ namespace _espe.repository.group
 		id : _espe.type.group_id
 	) : Promise<_espe.type.group_object>
 	{
-		const core_row : Record<string, any> = await get_store().read(id);
+		const row : Record<string, any> = await get_store().read(id);
 		
-		const dispersal : type_dispersal = {
-			"core_row": core_row,
-		};
+		const dispersal : type_dispersal = row;
 		
 		return decode(dispersal);
 	}
@@ -157,7 +151,7 @@ namespace _espe.repository.group
 		const dispersal : type_dispersal = encode(value);
 		
 		// core
-		const id : _espe.type.group_id = await get_store().create(dispersal.core_row);
+		const id : _espe.type.group_id = await get_store().create(dispersal);
 		
 		return id;
 	}
@@ -174,7 +168,7 @@ namespace _espe.repository.group
 		const dispersal : type_dispersal = encode(value);
 		
 		// core
-		await get_store().update(id, dispersal.core_row);		
+		await get_store().update(id, dispersal);		
 	}
 	
 	
diff --git a/source/repositories/invitation.ts b/source/repositories/invitation.ts
index 9042d72..78bf4e2 100644
--- a/source/repositories/invitation.ts
+++ b/source/repositories/invitation.ts
@@ -88,7 +88,7 @@ namespace _espe.repository.invitation
 				{
 					"database_implementation": _espe.helpers.database_implementation(),
 					"table_name": "invitation_groups",
-					"key_names": ["invitation_id","group_name"],
+					"key_names": ["invitation_id","group_id"],
 				}
 			);
 		}
@@ -128,8 +128,8 @@ namespace _espe.repository.invitation
 			"group_rows": (
 				(object.groups_value ?? [])
 				.map(
-					group => ({
-						"group_name": group,
+					group_id => ({
+						"group_id": group_id,
 					})
 				)
 			)
@@ -152,7 +152,7 @@ namespace _espe.repository.invitation
 			"email_address_value": dispersal.core_row["email_address_value"],
 			"groups_changeable": _espe.helpers.dbbool_decode(dispersal.core_row["groups_changeable"]),
 			"groups_value": lib_plankton.list.sorted<_espe.type.group_id>(
-				dispersal.group_rows.map(row => row["group_name"]),
+				dispersal.group_rows.map(row => row["group_id"]),
 				{
 					"compare_element": (group1, group2) => (group1 <= group2)
 				}
@@ -218,7 +218,7 @@ namespace _espe.repository.invitation
 			"core_row": core_row,
 			"group_rows": group_hits.map(
 				hit => ({
-					"group_name": hit.preview["group_name"]
+					"group_id": hit.preview["group_id"]
 				})
 			),
 		};
@@ -243,7 +243,7 @@ namespace _espe.repository.invitation
 			await get_group_chest().write(
 				[
 					id,
-					group_row["group_name"],
+					group_row["group_id"],
 				],
 				{
 					"_dummy": null,
diff --git a/source/sample.ts b/source/sample.ts
index cb9a93f..42e4500 100644
--- a/source/sample.ts
+++ b/source/sample.ts
@@ -93,7 +93,7 @@ namespace _espe.sample
 					{
 						"name": member_raw.name,
 						"email_address": member_raw.email_address,
-						"groups": member_raw.groups.map(track_groups.get),
+						"groups": member_raw.groups.map(group_id => track_groups.get(group_id)),
 					},
 					{
 						"silent": true,
@@ -115,7 +115,7 @@ namespace _espe.sample
 						"email_address_changeable": invitation_raw.email_address_changeable,
 						"email_address_value": invitation_raw.email_address_value,
 						"groups_changeable": invitation_raw.groups_changeable,
-						"groups_value": invitation_raw.groups_value.map(track_groups.get),
+						"groups_value": invitation_raw.groups_value.map(group_id => track_groups.get(group_id)),
 					}
 				);
 			}
diff --git a/source/services/group.ts b/source/services/group.ts
index 123b295..9ebd9f0 100644
--- a/source/services/group.ts
+++ b/source/services/group.ts
@@ -16,13 +16,43 @@ You should have received a copy of the GNU General Public License along with thi
 namespace _espe.service.group
 {
 	
+	/**
+	 */
+	export function list(
+	) : Promise<Array<{id : _espe.type.group_id; name : string;}>>
+	{
+		return _espe.repository.group.list(null);
+	}
+	
+	
+	/**
+	 */
+	export function get(
+		id : _espe.type.group_id
+	) : Promise<_espe.type.group_object>
+	{
+		return _espe.repository.group.read(id);
+	}
+	
+	
 	/**
 	 */
 	export function add(
-		group_object : _espe.type.group_object
+		object : _espe.type.group_object
 	) : Promise<_espe.type.group_id>
 	{
-		return _espe.repository.group.create(group_object);
+		return _espe.repository.group.create(object);
+	}
+	
+	
+	/**
+	 */
+	export function modify(
+		id : _espe.type.group_id,
+		object : _espe.type.group_object
+	) : Promise<void>
+	{
+		return _espe.repository.group.update(id, object);
 	}
 	
 }
diff --git a/tools/makefile b/tools/makefile
index 95edf91..14a7d0e 100644
--- a/tools/makefile
+++ b/tools/makefile
@@ -61,6 +61,10 @@ ${dir_temp}/espe-core.js ${dir_temp}/espe-core.d.ts: \
 		${dir_source}/api/actions/meta_spec.ts \
 		${dir_source}/api/actions/session_begin.ts \
 		${dir_source}/api/actions/session_end.ts \
+		${dir_source}/api/actions/group_list.ts \
+		${dir_source}/api/actions/group_read.ts \
+		${dir_source}/api/actions/group_add.ts \
+		${dir_source}/api/actions/group_modify.ts \
 		${dir_source}/api/actions/member_summon.ts \
 		${dir_source}/api/actions/member_list.ts \
 		${dir_source}/api/actions/member_read.ts \