diff --git a/core/attributedef/AttributeDBField.php b/core/attributedef/AttributeDBField.php
new file mode 100644
index 000000000..7e2d9954c
--- /dev/null
+++ b/core/attributedef/AttributeDBField.php
@@ -0,0 +1,24 @@
+<?php
+
+/**
+ * Base class for all kind of DB attributes, with the exception of external keys
+ *
+ * @package     iTopORM
+ */
+class AttributeDBField extends AttributeDBFieldVoid
+{
+    public static function ListExpectedParams()
+    {
+        return array_merge(parent::ListExpectedParams(), array("default_value", "is_null_allowed"));
+    }
+
+    public function GetDefaultValue(DBObject $oHostObject = null)
+    {
+        return $this->MakeRealValue($this->Get("default_value"), $oHostObject);
+    }
+
+    public function IsNullAllowed()
+    {
+        return $this->Get("is_null_allowed");
+    }
+}
\ No newline at end of file