diff --git a/controllers/class.AddDocument.php b/controllers/class.AddDocument.php
index ff61cafaf..1d9b6393a 100644
--- a/controllers/class.AddDocument.php
+++ b/controllers/class.AddDocument.php
@@ -56,7 +56,36 @@ class SeedDMS_Controller_AddDocument extends SeedDMS_Controller_Common {
 		$reqversion = $this->getParam('reqversion');
 		$version_comment = $this->getParam('versioncomment');
 		$attributes = $this->getParam('attributes');
+		foreach($attributes as $attrdefid=>$attribute) {
+			if($attrdef = $dms->getAttributeDefinition($attrdefid)) {
+				if(false === $this->callHook('validateAttribute', $attrdef, $attribute)) {
+					return false;
+				}
+				if($attribute) {
+					if(!$attrdef->validate($attribute)) {
+						$this->errormsg = getAttributeValidationError($attrdef->getValidationError(), $attrdef->getName(), $attribute);
+						return false;
+					}
+				} elseif($attrdef->getMinValues() > 0) {
+					$this->errormsg = array("attr_min_values", array("attrname"=>$attrdef->getName()));
+					return false;
+				}
+			}
+		}
 		$attributes_version = $this->getParam('attributesversion');
+		foreach($attributes_version as $attrdefid=>$attribute) {
+			if($attrdef = $dms->getAttributeDefinition($attrdefid)) {
+				if(false === $this->callHook('validateAttribute', $attrdef, $attribute)) {
+					return false;
+				}
+				if($attribute) {
+					if(!$attrdef->validate($attribute)) {
+						$this->errormsg = getAttributeValidationError($attrdef->getValidationError(), $attrdef->getName(), $attribute);
+						return false;
+					}
+				}
+			}
+		}
 		$workflow = $this->getParam('workflow');
 		$notificationgroups = $this->getParam('notificationgroups');
 		$notificationusers = $this->getParam('notificationusers');
diff --git a/controllers/class.AddSubFolder.php b/controllers/class.AddSubFolder.php
index 0d6582855..71f86f5b6 100644
--- a/controllers/class.AddSubFolder.php
+++ b/controllers/class.AddSubFolder.php
@@ -40,6 +40,22 @@ class SeedDMS_Controller_AddSubFolder extends SeedDMS_Controller_Common {
 		$comment = $this->getParam('comment');
 		$sequence = $this->getParam('sequence');
 		$attributes = $this->getParam('attributes');
+		foreach($attributes as $attrdefid=>$attribute) {
+			if($attrdef = $dms->getAttributeDefinition($attrdefid)) {
+				if(false === $this->callHook('validateAttribute', $attrdef, $attribute)) {
+					return false;
+				}
+				if($attribute) {
+					if(!$attrdef->validate($attribute)) {
+						$this->errormsg = getAttributeValidationError($attrdef->getValidationError(), $attrdef->getName(), $attribute);
+						return false;
+					}
+				} elseif($attrdef->getMinValues() > 0) {
+					$this->errormsg = array("attr_min_values", array("attrname"=>$attrdef->getName()));
+					return false;
+				}
+			}
+		}
 		$notificationgroups = $this->getParam('notificationgroups');
 		$notificationusers = $this->getParam('notificationusers');
 
diff --git a/controllers/class.EditDocument.php b/controllers/class.EditDocument.php
index 6d8714df4..d84ceae8d 100644
--- a/controllers/class.EditDocument.php
+++ b/controllers/class.EditDocument.php
@@ -116,22 +116,28 @@ class SeedDMS_Controller_EditDocument extends SeedDMS_Controller_Common {
 			$oldattributes = $document->getAttributes();
 			if($attributes) {
 				foreach($attributes as $attrdefid=>$attribute) {
-					$attrdef = $dms->getAttributeDefinition($attrdefid);
-					if($attribute) {
-						if(!$attrdef->validate($attribute)) {
-							$this->errormsg	= getAttributeValidationText($attrdef->getValidationError(), $attrdef->getName(), $attribute);
-							return false;
-						}
+					if($attrdef = $dms->getAttributeDefinition($attrdefid)) {
+						if(null === ($ret = $this->callHook('validateAttribute', $attrdef, $attribute))) {
+						if($attribute) {
+							if(!$attrdef->validate($attribute)) {
+								$this->errormsg	= getAttributeValidationError($attrdef->getValidationError(), $attrdef->getName(), $attribute);
+								return false;
+							}
 
-						if(!isset($oldattributes[$attrdefid]) || $attribute != $oldattributes[$attrdefid]->getValue()) {
-							if(!$document->setAttributeValue($dms->getAttributeDefinition($attrdefid), $attribute))
+							if(!isset($oldattributes[$attrdefid]) || $attribute != $oldattributes[$attrdefid]->getValue()) {
+								if(!$document->setAttributeValue($dms->getAttributeDefinition($attrdefid), $attribute))
+									return false;
+							}
+						} elseif($attrdef->getMinValues() > 0) {
+							$this->errormsg = array("attr_min_values", array("attrname"=>$attrdef->getName()));
+						} elseif(isset($oldattributes[$attrdefid])) {
+							if(!$document->removeAttribute($dms->getAttributeDefinition($attrdefid)))
+								return false;
+						}
+						} else {
+							if($ret === false)
 								return false;
 						}
-					} elseif($attrdef->getMinValues() > 0) {
-						$this->errormsg = getMLText("attr_min_values", array("attrname"=>$attrdef->getName()));
-					} elseif(isset($oldattributes[$attrdefid])) {
-						if(!$document->removeAttribute($dms->getAttributeDefinition($attrdefid)))
-							return false;
 					}
 				}
 			}
diff --git a/controllers/class.EditFolder.php b/controllers/class.EditFolder.php
index f41399fe5..02c6d1163 100644
--- a/controllers/class.EditFolder.php
+++ b/controllers/class.EditFolder.php
@@ -51,6 +51,7 @@ class SeedDMS_Controller_EditFolder extends SeedDMS_Controller_Common {
 			if($attributes) {
 				foreach($attributes as $attrdefid=>$attribute) {
 					$attrdef = $dms->getAttributeDefinition($attrdefid);
+					if(null === ($ret = $this->callHook('validateAttribute', $attrdef, $attribute))) {
 					if($attribute) {
 						if(!$attrdef->validate($attribute)) {
 							$this->errormsg	= getAttributeValidationText($attrdef->getValidationError(), $attrdef->getName(), $attribute);
@@ -67,6 +68,10 @@ class SeedDMS_Controller_EditFolder extends SeedDMS_Controller_Common {
 						if(!$folder->removeAttribute($dms->getAttributeDefinition($attrdefid)))
 							return false;
 					}
+					} else {
+						if($ret === false)
+							return false;
+					}
 				}
 			}
 			foreach($oldattributes as $attrdefid=>$oldattribute) {
diff --git a/op/op.AddDocument.php b/op/op.AddDocument.php
index 5cc09cc88..a82105aa5 100644
--- a/op/op.AddDocument.php
+++ b/op/op.AddDocument.php
@@ -93,6 +93,7 @@ if(isset($_POST["attributes"]))
 	$attributes = $_POST["attributes"];
 else
 	$attributes = array();
+/* Has been moved to controller
 foreach($attributes as $attrdefid=>$attribute) {
 	if($attrdef = $dms->getAttributeDefinition($attrdefid)) {
 		if($attribute) {
@@ -105,11 +106,13 @@ foreach($attributes as $attrdefid=>$attribute) {
 		}
 	}
 }
+ */
 
 if(isset($_POST["attributes_version"]))
 	$attributes_version = $_POST["attributes_version"];
 else
 	$attributes_version = array();
+/* Has been moved to controller
 foreach($attributes_version as $attrdefid=>$attribute) {
 	$attrdef = $dms->getAttributeDefinition($attrdefid);
 	if($attribute) {
@@ -119,6 +122,7 @@ foreach($attributes_version as $attrdefid=>$attribute) {
 		}
 	}
 }
+ */
 
 $reqversion = (int)$_POST["reqversion"];
 if ($reqversion<1) $reqversion=1;
@@ -387,7 +391,15 @@ for ($file_num=0;$file_num<count($_FILES["userfile"]["tmp_name"]);$file_num++){
 	$controller->setParam('defaultaccessdocs', $settings->_defaultAccessDocs);
 
 	if(!$document = $controller->run()) {
-		UI::exitError(getMLText("folder_title", array("foldername" => $folder->getName())),getMLText($controller->getErrorMsg()));
+		$err = $controller->getErrorMsg();
+		if(is_string($err))
+			$errmsg = getMLText($err);
+		elseif(is_array($err)) {
+			$errmsg = getMLText($err[0], $err[1]);
+		} else {
+			$errmsg = $err;
+		}
+		UI::exitError(getMLText("folder_title", array("foldername" => $folder->getName())),$errmsg);
 	} else {
 		// Send notification to subscribers of folder.
 		if($notifier) {
diff --git a/op/op.AddSubFolder.php b/op/op.AddSubFolder.php
index f0284d1cb..19012dd46 100644
--- a/op/op.AddSubFolder.php
+++ b/op/op.AddSubFolder.php
@@ -67,6 +67,7 @@ if(isset($_POST["attributes"]))
 	$attributes = $_POST["attributes"];
 else
 	$attributes = array();
+/*
 foreach($attributes as $attrdefid=>$attribute) {
 	$attrdef = $dms->getAttributeDefinition($attrdefid);
 	if($attribute) {
@@ -78,6 +79,7 @@ foreach($attributes as $attrdefid=>$attribute) {
 		UI::exitError(getMLText("folder_title", array("foldername" => $document->getName())),getMLText("attr_min_values", array("attrname"=>$attrdef->getName())));
 	}
 }
+ */
 
 /* Check if additional notification shall be added */
 $notusers = array();
diff --git a/op/op.EditDocument.php b/op/op.EditDocument.php
index 5c3a66d4f..a8ef4fbc4 100644
--- a/op/op.EditDocument.php
+++ b/op/op.EditDocument.php
@@ -127,9 +127,15 @@ $controller->setParam('expires', $expires);
 $controller->setParam('sequence', $sequence);
 $controller->setParam('attributes', $attributes);
 if(!$controller->run()) {
-	if($controller->getErrorMsg()) {
-		UI::exitError(getMLText("document_title", array("documentname" => $document->getName())), $controller->getErrorMsg());
+	$err = $controller->getErrorMsg();
+	if(is_string($err))
+		$errmsg = getMLText($err);
+	elseif(is_array($err)) {
+		$errmsg = getMLText($err[0], $err[1]);
+	} else {
+		$errmsg = $err;
 	}
+	UI::exitError(getMLText("document_title", array("documentname" => $document->getName())), $errmsg);
 }
 
 if ($oldname != $name) {
diff --git a/op/op.EditFolder.php b/op/op.EditFolder.php
index 050d6b3f5..6ea93f654 100644
--- a/op/op.EditFolder.php
+++ b/op/op.EditFolder.php
@@ -80,9 +80,15 @@ $controller->setParam('comment', $comment);
 $controller->setParam('sequence', $sequence);
 $controller->setParam('attributes', $attributes);
 if(!$controller->run()) {
-	if($controller->getErrorMsg()) {
-		UI::exitError(getMLText("folder_title", array("foldername" => $folder->getName())), $controller->getErrorMsg());
+	$err = $controller->getErrorMsg();
+	if(is_string($err))
+		$errmsg = getMLText($err);
+	elseif(is_array($err)) {
+		$errmsg = getMLText($err[0], $err[1]);
+	} else {
+		$errmsg = $err;
 	}
+	UI::exitError(getMLText("folder_title", array("foldername" => $folder->getName())), $errmsg);
 }
 
 if($oldname != $name) {