diff --git a/interface-spec.html b/interface-spec.html
index 8834b9a..36c6101 100644
--- a/interface-spec.html
+++ b/interface-spec.html
@@ -106,6 +106,10 @@ <h2>Design elements and principles</h2>
     </li>
     <li>Should allow "upgrading" a plain object into a fully functional triple</li>
     <li>Interfaces may have additional implementation specific properties.</li>
+    <li>
+       We don't define any validation of given values (e.g. IRI, URI, CURIE). 
+       Implementations that apply validation should make this fact clear in their documentation.
+    </li>
   </ul>
 
   <p>