diff --git a/application/cmdbabstract.class.inc.php b/application/cmdbabstract.class.inc.php
index 1a8522c7d..804aeb67f 100644
--- a/application/cmdbabstract.class.inc.php
+++ b/application/cmdbabstract.class.inc.php
@@ -232,26 +232,25 @@ EOF
 	 * last plugin to set the message for a given message id) In practice, standard messages are recorded at the end
 	 * but they will not overwrite existing messages
 	 *
+	 * @see SetSessionMessageFromInstance() to call from within an instance
+	 *
 	 * @param string $sClass The class of the object (must be the final class)
 	 * @param int $iKey The identifier of the object
 	 * @param string $sMessageId Your id or one of the well-known ids: 'create', 'update' and 'apply_stimulus'
 	 * @param string $sMessage The HTML message (must be correctly escaped)
-	 * @param string $sSeverity Any of the following: ok, info, error.
+	 * @param string $sSeverity Any of the \WebPage::ENUM_SESSION_MESSAGE_SEVERITY_XXX constants
 	 * @param float $fRank Ordering of the message: smallest displayed first (can be negative)
 	 * @param bool $bMustNotExist Do not alter any existing message (considering the id)
 	 *
-	 * @see SetSessionMessageFromInstance() to call from within an instance
+	 * @return void
 	 */
-	public static function SetSessionMessage(
-		$sClass, $iKey, $sMessageId, $sMessage, $sSeverity, $fRank, $bMustNotExist = false
-	) {
+	public static function SetSessionMessage($sClass, $iKey, $sMessageId, $sMessage, $sSeverity, $fRank, $bMustNotExist = false)
+	{
 		$sMessageKey = $sClass.'::'.$iKey;
-		if (!isset($_SESSION['obj_messages'][$sMessageKey]))
-		{
+		if (!isset($_SESSION['obj_messages'][$sMessageKey])) {
 			$_SESSION['obj_messages'][$sMessageKey] = array();
 		}
-		if (!$bMustNotExist || !array_key_exists($sMessageId, $_SESSION['obj_messages'][$sMessageKey]))
-		{
+		if (!$bMustNotExist || !array_key_exists($sMessageId, $_SESSION['obj_messages'][$sMessageKey])) {
 			$_SESSION['obj_messages'][$sMessageKey][$sMessageId] = array(
 				'rank' => $fRank,
 				'severity' => $sSeverity,
diff --git a/sources/application/WebPage/WebPage.php b/sources/application/WebPage/WebPage.php
index 28681b16a..c21530983 100644
--- a/sources/application/WebPage/WebPage.php
+++ b/sources/application/WebPage/WebPage.php
@@ -50,6 +50,34 @@ class WebPage implements Page
 	 * @since 2.7.0 N°2529
 	 */
 	const PAGES_CHARSET = 'utf-8';
+
+	/**
+	 * @var string
+	 * @since 3.0.0
+	 */
+	public const ENUM_SESSION_MESSAGE_SEVERITY_INFO = 'INFO';
+	/**
+	 * @var string
+	 * @since 3.0.0
+	 */
+	public const ENUM_SESSION_MESSAGE_SEVERITY_OK = 'ok';
+	/**
+	 * @var string
+	 * @since 3.0.0
+	 */
+	public const ENUM_SESSION_MESSAGE_SEVERITY_WARNING = 'warning';
+	/**
+	 * @var string
+	 * @since 3.0.0
+	 */
+	public const ENUM_SESSION_MESSAGE_SEVERITY_ERROR = 'error';
+
+
+	/**
+	 * @var string
+	 * @since 3.0.0
+	 */
+	public const DEFAULT_SESSION_MESSAGE_SEVERITY = self::ENUM_SESSION_MESSAGE_SEVERITY_INFO;
 	const DEFAULT_PAGE_TEMPLATE_REL_PATH = 'pages/backoffice/webpage/layout';
 
 	protected $s_title;
@@ -92,7 +120,6 @@ class WebPage implements Page
 	protected $sTemplateRelPath;
 
 
-
 	/**
 	 * @var bool|string|string[]
 	 */
@@ -150,16 +177,16 @@ class WebPage implements Page
 					$aReadMessages[] = $aMessageData['message'];
 					$aRanks[] = $aMessageData['rank'];
 					switch ($aMessageData['severity']) {
-						case 'ok':
+						case static::ENUM_SESSION_MESSAGE_SEVERITY_OK:
 							$aMessages[] = AlertUIBlockFactory::MakeForSuccess('', $aMessageData['message']);
 							break;
-						case 'warning':
+						case static::ENUM_SESSION_MESSAGE_SEVERITY_WARNING:
 							$aMessages[] = AlertUIBlockFactory::MakeForWarning('', $aMessageData['message']);
 							break;
-						case 'error':
+						case static::ENUM_SESSION_MESSAGE_SEVERITY_ERROR:
 							$aMessages[] = AlertUIBlockFactory::MakeForDanger('', $aMessageData['message']);
 							break;
-						case 'info':
+						case static::ENUM_SESSION_MESSAGE_SEVERITY_INFO:
 						default:
 							$aMessages[] = AlertUIBlockFactory::MakeForInformation('', $aMessageData['message']);
 							break;