diff --git a/core/trunk/core/xml/datatypes.xsd b/core/trunk/core/xml/datatypes.xsd
index ce12c8db3b879a5e3eadf6a4e5c711d32bd98134..378fe1d760dc6510bf64333a34ed13bfe3eaccd4 100644
--- a/core/trunk/core/xml/datatypes.xsd
+++ b/core/trunk/core/xml/datatypes.xsd
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <xsd:schema 
   xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
+  xmlns:das="maarch:DataAccessService" 
   elementFormDefault="qualified"  
   >
   
@@ -77,7 +78,7 @@
   
   <!-- Datetime --> 
   <xsd:simpleType name="datetime">
-    <xsd:union memberTypes="xsd:date xsd:time xsd:string"/>
+    <xsd:union memberTypes="xsd:date xsd:time xsd:string" das:baseType="xsd:string"/>
   </xsd:simpleType>
 
 </xsd:schema>