diff --git a/application/src/Domain/AbstractDomainService.php b/application/src/Domain/AbstractDomainService.php
new file mode 100644
index 0000000..8992f3a
--- /dev/null
+++ b/application/src/Domain/AbstractDomainService.php
@@ -0,0 +1,7 @@
+<?php
+namespace App\Domain;
+
+abstract class AbstractDomainService
+{
+}
+
diff --git a/application/src/Domain/SourceManagement/AbstractSourceService.php b/application/src/Domain/SourceManagement/AbstractSourceService.php
new file mode 100644
index 0000000..9ec2d46
--- /dev/null
+++ b/application/src/Domain/SourceManagement/AbstractSourceService.php
@@ -0,0 +1,9 @@
+<?php
+namespace App\Domain\SourceManagement;
+
+use App\Domain\AbstractDomainService;
+
+abstract class AbstractSourceService extends AbstractDomainService
+{
+}
+
diff --git a/application/src/Domain/SourceManagement/TreeSourceService.php b/application/src/Domain/SourceManagement/TreeSourceService.php
new file mode 100644
index 0000000..e00adea
--- /dev/null
+++ b/application/src/Domain/SourceManagement/TreeSourceService.php
@@ -0,0 +1,98 @@
+<?php
+namespace App\Domain\SourceManagement;
+
+use App\Entity\Source\Collection\TreeCollectionSourceInterface;
+use App\Entity\Source\Collection\TreeCollectionSource;
+use Doctrine\Common\Collections\Collection;
+use Doctrine\Common\Collections\ArrayCollection;
+use App\Entity\Source\SourceInterface;
+
+/**
+ * 
+ * Allows to iterate over a tree
+ * @author kevinfrantz
+ * @todo Maybe lazy loading would be helpfull for performance
+ */
+class TreeSourceService extends AbstractSourceService implements TreeSourceServiceInterface
+{
+    /**
+     * @var TreeCollectionSourceInterface
+     */
+    private $source;
+    
+    /**
+     * Containes all branches of the actual level of the tree
+     * @var Collection
+     */
+    private $branches;
+    
+    /**
+     * Containes all leaves of the actual level of the tree
+     * @var Collection
+     */
+    private $leaves;
+    
+    public function __construct(TreeCollectionSource $source){
+        $this->source = $source;
+        $this->branches = new ArrayCollection();
+        $this->leaves = new ArrayCollection();
+    }
+    
+    private function sortMember(SourceInterface $member):bool{
+        if($member instanceof TreeCollectionSource){
+            return $this->branches->add($member);
+        }
+        return $this->leaves->add($member);
+    }
+    
+    private function basicSort():void{
+        foreach($this->source->getCollection() as $member){
+            $this->sortMember($member);        
+        }
+    }
+    
+    public function getBranches(): Collection
+    {
+        return $this->branches;
+    }
+
+    /**
+     * @todo Remove the optional parameter and put the logic in a private funtion.
+     * @todo Remove the getAllBranches use inside the function. 
+     * {@inheritDoc}
+     * @see \App\Domain\SourceManagement\TreeSourceServiceInterface::getAllBranches()
+     */
+    public function getAllBranches(?ArrayCollection $excludedBranches=null): Collection
+    {
+        if(!$excludedBranches){
+            $excludedBranches = new ArrayCollection();
+        }
+        $branches = new ArrayCollection($this->branches->toArray());
+        foreach($this->branches->toArray() as $branch){
+            if(!$excludedBranches->contains($branch)){
+                foreach((new TreeSourceService($branch))->getAllBranches($excludedBranches) as $branchBranch){
+                    $branches->add($branchBranch);
+                }
+            }
+        }
+        return $branches;
+    }
+    
+    public function getLeaves(): Collection
+    {
+        return $this->leaves;
+    }
+
+    public function getAllLeaves(): Collection
+    {
+        $leaves = new ArrayCollection();
+        foreach ($this->getAllBranches()->toArray() as $branch){
+            foreach ((new TreeSourceService($branch))->getLeaves() as $leave){
+                if(!$leaves->contains($leave)){
+                    $leaves->add($leave);
+                }
+            }
+        }
+    }
+ 
+}
\ No newline at end of file
diff --git a/application/src/Domain/SourceManagement/TreeSourceServiceInterface.php b/application/src/Domain/SourceManagement/TreeSourceServiceInterface.php
new file mode 100644
index 0000000..8aa7da9
--- /dev/null
+++ b/application/src/Domain/SourceManagement/TreeSourceServiceInterface.php
@@ -0,0 +1,32 @@
+<?php
+namespace App\Domain\SourceManagement;
+
+use Doctrine\Common\Collections\Collection;
+
+interface TreeSourceServiceInterface
+{
+    /**
+     * Delivers the branches of the actual tree back
+     * @return Collection
+     */
+    public function getBranches():Collection;
+    
+    /**
+     * Delivers the members of the actual tree back
+     * @return Collection
+     */
+    public function getLeaves():Collection;
+    
+    /**
+     * Delivers all members till a infinite level of the tree back
+     * @return Collection
+     */
+    public function getAllLeaves():Collection;
+    
+    /**
+     * Delivers all branches till a infinite level of the actual tree back
+     * @return Collection
+     */
+    public function getAllBranches():Collection;
+}
+
diff --git a/application/src/Exception/NotSortableException.php b/application/src/Exception/NotSortableException.php
new file mode 100644
index 0000000..3120670
--- /dev/null
+++ b/application/src/Exception/NotSortableException.php
@@ -0,0 +1,6 @@
+<?php
+namespace App\Exception;
+
+class NotSortableException extends \Exception
+{
+}
\ No newline at end of file