diff --git a/classes/chunkupload_form_element.php b/classes/chunkupload_form_element.php
index 42b3842..82102d8 100644
--- a/classes/chunkupload_form_element.php
+++ b/classes/chunkupload_form_element.php
@@ -115,7 +115,7 @@ public function tohtml() {
         if ($value = $this->getvalue()) {
             global $DB;
             if ($record = $DB->get_record('local_chunkupload_files', ['id' => $value])) {
-                if ($record->state == 2) {
+                if ($record->state == state_type::UPLOAD_COMPLETED) {
                     $filenamestring = $record->filename;
                     $showfinishedicon = true;
                 }
@@ -202,10 +202,10 @@ public function validatesubmitvalue($value) {
             return "";
         }
         $record = $DB->get_record('local_chunkupload_files', ['id' => $value]);
-        if (!$record || $record->state == 0) {
+        if (!$record || $record->state == state_type::UNUSED_TOKEN_GENERATED) {
             return "";
         }
-        if ($record->state == 1) {
+        if ($record->state == state_type::UPLOAD_STARTED) {
             return get_string('uploadnotfinished', 'local_chunkupload');
         }
         $path = self::get_path_for_id($value);
@@ -292,7 +292,7 @@ public static function export_to_filearea($chunkuploadid, $newcontextid, $newcom
         global $DB;
         $fs = get_file_storage();
         $record = $DB->get_record('local_chunkupload_files', ['id' => $chunkuploadid], '*', IGNORE_MISSING);
-        if (!$record || $record->state !== 2) {
+        if (!$record || $record->state !== state_type::UPLOAD_COMPLETED) {
             return null;
         }
 
@@ -338,7 +338,7 @@ public static function is_file_uploaded($id) {
             return false;
         }
 
-        if (!$record->state == 2) {
+        if (!$record->state == state_type::UPLOAD_COMPLETED) {
             return false;
         }
         return true;
diff --git a/classes/state_type.php b/classes/state_type.php
new file mode 100644
index 0000000..d0b6b2f
--- /dev/null
+++ b/classes/state_type.php
@@ -0,0 +1,44 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle 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.
+//
+// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Defines available state_types.
+ * @package    local_chunkupload
+ * @copyright  2020 Laura Troost, Nina Herrmann WWU
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+namespace local_chunkupload;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Defines available state_types.
+ * @package    local_chunkupload
+ * @copyright  2020 Laura Troost, Nina Herrmann WWU
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class state_type {
+
+    /** @var string Represents the type for a step subplugin. 0: token generated, not used; 1: file upload started;
+     * 2: file upload completed
+     */
+    const UNUSED_TOKEN_GENERATED = 0;
+    /** @var string Represents the type for a trigger subplugin. */
+    const UPLOAD_STARTED = 1;
+    /** @var string Represents the type for a trigger subplugin. */
+    const UPLOAD_COMPLETED = 2;
+
+}
diff --git a/classes/task/cleanup_files.php b/classes/task/cleanup_files.php
index 2c5ce57..ac35dfb 100644
--- a/classes/task/cleanup_files.php
+++ b/classes/task/cleanup_files.php
@@ -25,6 +25,7 @@
 namespace local_chunkupload\task;
 
 use local_chunkupload\chunkupload_form_element;
+use local_chunkupload\state_type;
 
 /**
  * Chunkupload Cleanup Task
@@ -51,13 +52,14 @@ public function execute() {
         global $DB;
         $config = get_config('local_chunkupload');
 
-        // State 0.
-        $DB->delete_records_select('local_chunkupload_files', 'state = 0 AND lastmodified < :time',
-                array('time' => time() - $config->state0duration));
+        // State UNUSED_TOKEN_GENERATED 0.
+        $DB->delete_records_select('local_chunkupload_files', 'state = :state AND lastmodified < :time',
+                array('time' => time() - $config->state0duration, 'state' => state_type::UNUSED_TOKEN_GENERATED));
 
-        // State 1.
+        // State UPLOAD_STARTED 1.
         $ids = $DB->get_fieldset_select('local_chunkupload_files', 'id',
-                'lastmodified < :time AND state = 1', array('time' => time() - $config->state1duration));
+                'lastmodified < :time AND state = :state', array('time' => time() - $config->state1duration,
+                'state' => state_type::UPLOAD_STARTED));
         $DB->delete_records_list('local_chunkupload_files', 'id', $ids);
         foreach ($ids as $id) {
             $path = chunkupload_form_element::get_path_for_id($id);
@@ -66,9 +68,10 @@ public function execute() {
             }
         }
 
-        // State 2.
+        // State UPLOAD_COMPLETED 2.
         $ids = $DB->get_fieldset_select('local_chunkupload_files', 'id',
-                'lastmodified < :time AND state = 2', array('time' => time() - $config->state2duration));
+                'lastmodified < :time AND state = :state', array('time' => time() - $config->state2duration,
+                'state' => state_type::UPLOAD_COMPLETED));
         $DB->delete_records_list('local_chunkupload_files', 'id', $ids);
         foreach ($ids as $id) {
             $path = chunkupload_form_element::get_path_for_id($id);
diff --git a/deleteupload_ajax.php b/deleteupload_ajax.php
index 15e0472..381fc5f 100644
--- a/deleteupload_ajax.php
+++ b/deleteupload_ajax.php
@@ -70,7 +70,7 @@
     $record->currentpos = 0;
     $record->length = 0;
     $record->lastmodified = time();
-    $record->state = 0;
+    $record->state = \local_chunkupload\state_type::UNUSED_TOKEN_GENERATED;
     $record->filename = "";
     $DB->update_record('local_chunkupload_files', $record);
 }
diff --git a/proceedupload_ajax.php b/proceedupload_ajax.php
index b5da8b5..4cdb327 100644
--- a/proceedupload_ajax.php
+++ b/proceedupload_ajax.php
@@ -82,7 +82,7 @@
     die(json_encode($err));
 }
 
-if ($record->state != 1) {
+if ($record->state != \local_chunkupload\state_type::UPLOAD_STARTED) {
     $err->error = "File is in state $record->state, unable to proceed upload!";
     die(json_encode($err));
 }
@@ -113,7 +113,8 @@
 
 file_put_contents($path, $content, FILE_APPEND);
 
-$record->state = $end == $record->length ? 2 : 1;
+$record->state = $end == $record->length ? \local_chunkupload\state_type::UPLOAD_COMPLETED :
+    \local_chunkupload\state_type::UPLOAD_STARTED;
 $record->currentpos = $end;
 $record->lastmodified = time();
 
diff --git a/startupload_ajax.php b/startupload_ajax.php
index 43699dc..40b8f38 100644
--- a/startupload_ajax.php
+++ b/startupload_ajax.php
@@ -106,7 +106,8 @@
 $filerecord->currentpos = $end;
 $filerecord->length = $length;
 $filerecord->lastmodified = time();
-$filerecord->state = $end == $length ? 2 : 1;
+$filerecord->state = $end == $length ? \local_chunkupload\state_type::UPLOAD_COMPLETED :
+    \local_chunkupload\state_type::UPLOAD_STARTED;
 $filerecord->filename = $filename;
 $DB->update_record('local_chunkupload_files', $filerecord);