diff --git a/lib/OrganisationProvider/OrganisationProvider.php b/lib/OrganisationProvider/OrganisationProvider.php
index f94726e..2455ba7 100644
--- a/lib/OrganisationProvider/OrganisationProvider.php
+++ b/lib/OrganisationProvider/OrganisationProvider.php
@@ -11,5 +11,37 @@ abstract class OrganizationProvider {
 		return $this->id;
 	}
 
-	// TODO: functions to access organisation structure
+	/* Return one level of the Organization Tree */
+   /*
+   *        ┌────────────────────────────┐                                           
+   *        │         Root Node          │                                           
+   *        │ (of Organization Provider) │                                           
+   *        └──┬──────────────────────┬──┘                                           
+   *           │                      │                                              
+   *           │                      │                                              
+   * ┌── ── ── │── ── ── ── ── ── ── ─│─ ── ── ─┐                                    
+   *           │                      │                                              
+   * │         ▼                      ▼         │                                    
+   *    ┌──────────────┐      ┌──────────────┐                                       
+   * │  │              │      │              │  │                                    
+   *    │Organization 1│      │Organization 2│    ◄── ── ── getOrganizations();      
+   * │  │              │      │              │  │                                    
+   *    └┬────────────┬┘      └┬────────────┬┘                                       
+   * │   │            │        │            │   │                                    
+   *     │            │        │            │                                        
+   * └── ├─ ── ── ── ─┤ ── ── ─┼ ── ── ── ──│── ┘                                    
+   *     │            │        │            │                                        
+   *     ▼            ▼        │            │                                        
+   *    ...          ...       ▼            ▼                                        
+   *                 ┌── ── ── ── ── ── ── ── ── ── ─┐                               
+   *                   ┌────────────┐ ┌────────────┐                                 
+   *                 │ │            │ │            │ │                               
+   *                   │ Suborg. 21 │ │ Suborg. 22 │   ◄── ── ── getOrganizations(2);
+   *                 │ │            │ │            │ │                               
+   *                   └────────────┘ └────────────┘                                 
+   *                 └── ── ── ── ── ── ── ── ── ── ─┘                               
+   */
+	abstract public function getOrganizations(?int $parentOrganizationId);
+
+	abstract public function getRolesOfOrganization(int $organizationId);
 }
\ No newline at end of file