diff --git a/src/Db/AttrSet.php b/src/Db/AttrSet.php
new file mode 100644
index 0000000..33cefc7
--- /dev/null
+++ b/src/Db/AttrSet.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace EesyPHP\Db;
+
+class AttrSet extends Attr {
+
+  /**
+   * Possible values
+   * @var array<mixed>
+   */
+  protected $possible_values = [];
+
+  /**
+   * Compute attribute value from DB
+   * @param string|null $value  The value as retrieved from debug
+   * @return string|null The attribute value
+   */
+  public function from_db($value) {
+    $value = parent::from_db($value);
+    if (is_null($value))
+      return null;
+    if (!in_array($value, $this -> possible_values))
+      throw new DbException(
+        "Unexpected value '%s' retrieved from database. Should be one of the following values: %s",
+        $value, implode(', ', $this -> possible_values)
+      );
+    return $value;
+  }
+
+  /**
+   * Compute attribute value for DB
+   * @param string|null $value  The value as handled in PHP
+   * @return string|null The attribute value as stored in DB
+   */
+  public function to_db($value) {
+    $value = parent::from_db($value);
+    if (is_null($value))
+      return null;
+    if (!in_array($value, $this -> possible_values))
+      throw new DbException(
+        "Unexpected value '%s'. Should be one of the following values: %s",
+        $value, implode(', ', $this -> possible_values)
+      );
+    return $value;
+  }
+
+}