diff --git a/src/models/entities/Permission.ts b/src/models/entities/Permission.ts
index b9e2777..86f7d6a 100644
--- a/src/models/entities/Permission.ts
+++ b/src/models/entities/Permission.ts
@@ -1,12 +1,11 @@
 import {
   IsInt,
-  IsNotEmpty,
-
-  IsString
+  IsNotEmpty
 } from "class-validator";
-import { Column, Entity, OneToMany, PrimaryGeneratedColumn } from "typeorm";
-import { User } from './User';
-import { UserGroup } from './UserGroup';
+import { Column, Entity, ManyToOne, PrimaryGeneratedColumn } from "typeorm";
+import { PermissionAction } from '../enums/PermissionAction';
+import { PermissionTarget } from '../enums/PermissionTargets';
+import { Principal } from './Principal';
 /**
  * Defines the Permission interface.
 */
@@ -20,30 +19,27 @@ export abstract class Permission {
   id: number;
 
   /**
-   * users
+   * The permissions principal
    */
-  @OneToMany(() => User, user => user.permissions, { nullable: true })
-  users: User[]
-
-  /**
-   * groups
-   */
-  @OneToMany(() => UserGroup, group => group.permissions, { nullable: true })
-  groups: UserGroup[]
+  @ManyToOne(() => Principal, principal => principal.permissions)
+  principal: Principal[]
 
   /**
    * The target
    */
-  @Column()
+  @Column({
+    type: 'simple-enum',
+    enum: PermissionTarget
+  })
   @IsNotEmpty()
-  @IsString()
-  target: string;
+  target: PermissionTarget;
 
   /**
    * The action type
    */
-  @Column()
-  @IsNotEmpty()
-  @IsString()
-  action: string;
+  @Column({
+    type: 'simple-enum',
+    enum: PermissionAction
+  })
+  action: PermissionAction;
 }
\ No newline at end of file
diff --git a/src/models/entities/Principal.ts b/src/models/entities/Principal.ts
new file mode 100644
index 0000000..f1242b5
--- /dev/null
+++ b/src/models/entities/Principal.ts
@@ -0,0 +1,24 @@
+import { IsInt, IsOptional } from 'class-validator';
+import { Entity, OneToMany, PrimaryGeneratedColumn, TableInheritance } from 'typeorm';
+import { Permission } from './Permission';
+
+/**
+ * Defines a admin user.
+*/
+@Entity()
+@TableInheritance({ column: { name: "type", type: "varchar" } })
+export abstract class Principal {
+  /**
+  * autogenerated unique id (primary key).
+  */
+  @PrimaryGeneratedColumn()
+  @IsInt()
+  id: number;
+
+  /**
+* permissions
+*/
+  @IsOptional()
+  @OneToMany(() => Permission, permission => permission.principal, { nullable: true })
+  permissions?: Permission[];
+}
\ No newline at end of file
diff --git a/src/models/entities/User.ts b/src/models/entities/User.ts
index ebc62b1..2b5b9b3 100644
--- a/src/models/entities/User.ts
+++ b/src/models/entities/User.ts
@@ -1,22 +1,16 @@
 import { IsBoolean, IsEmail, IsInt, IsNotEmpty, IsOptional, IsPhoneNumber, IsString, IsUUID } from "class-validator";
-import { Column, Entity, JoinTable, ManyToMany, ManyToOne, OneToMany, PrimaryGeneratedColumn } from "typeorm";
+import { ChildEntity, Column, JoinTable, ManyToMany, OneToMany } from "typeorm";
 import { config } from '../../config';
 import { Permission } from './Permission';
+import { Principal } from './Principal';
 import { UserAction } from './UserAction';
 import { UserGroup } from './UserGroup';
 
 /**
  * Defines a admin user.
 */
-@Entity()
-export class User {
-  /**
-  * autogenerated unique id (primary key).
-  */
-  @PrimaryGeneratedColumn()
-  @IsInt()
-  id: number;
-
+@ChildEntity()
+export class User extends Principal {
   /**
   * uuid
   */
@@ -78,13 +72,6 @@ export class User {
   @IsNotEmpty()
   password: string;
 
-  /**
-  * permissions
-  */
-  @IsOptional()
-  @ManyToOne(() => Permission, permission => permission.users, { nullable: true })
-  permissions?: Permission[];
-
   /**
   * groups
   */
diff --git a/src/models/entities/UserGroup.ts b/src/models/entities/UserGroup.ts
index e86b2a6..21dfe25 100644
--- a/src/models/entities/UserGroup.ts
+++ b/src/models/entities/UserGroup.ts
@@ -1,29 +1,16 @@
 import {
-  IsInt,
   IsNotEmpty,
   IsOptional,
   IsString
 } from "class-validator";
-import { Column, Entity, ManyToOne, PrimaryGeneratedColumn } from "typeorm";
-import { Permission } from "./Permission";
+import { ChildEntity, Column } from "typeorm";
+import { Principal } from './Principal';
 
 /**
  * Defines the UserGroup interface.
 */
-@Entity()
-export class UserGroup {
-  /**
-   * Autogenerated unique id (primary key).
-   */
-  @PrimaryGeneratedColumn()
-  @IsInt()
-  id: number;
-
-  /**
-     * permissions
-     */
-  @ManyToOne(() => Permission, permission => permission.groups, { nullable: true })
-  permissions: Permission[];
+@ChildEntity()
+export class UserGroup extends Principal {
 
   /**
    * The group's name
diff --git a/src/models/enums/PermissionAction.ts b/src/models/enums/PermissionAction.ts
new file mode 100644
index 0000000..8ea9e65
--- /dev/null
+++ b/src/models/enums/PermissionAction.ts
@@ -0,0 +1,6 @@
+export enum PermissionAction {
+    READ = 'READ',
+    ADD = 'ADD',
+    UPDATE = 'UPDATE',
+    DELETE = 'DELETE'
+}
\ No newline at end of file
diff --git a/src/models/enums/PermissionTargets.ts b/src/models/enums/PermissionTargets.ts
new file mode 100644
index 0000000..9a6f040
--- /dev/null
+++ b/src/models/enums/PermissionTargets.ts
@@ -0,0 +1,8 @@
+export enum PermissionTarget {
+    RUNNER = 'RUNNER',
+    ORGANISATION = 'RUNNERORGANISATION',
+    TEAM = 'RUNNERTEAM',
+    TRACK = 'TRACK',
+    USER = 'USER',
+    GROUP = 'USERGROUP'
+}
\ No newline at end of file