Use of configuration-point to inject a service-point

[Stephane Decleire]

Are those configurations equivalent ?

1.
   <service-point id="RubricHierarchyFactory" 
interface="org.apache.tapestry.engine.state.StateObjectFactory">
       <invoke-factory>
           <construct 
class="com.cariboonetworks.ads.services.impl.RubricHierarchyFactory">
               <set-object property="root" value="service:RubricAd"/>
           </construct>
       </invoke-factory>
   </service-point>
2.
   <service-point id="RubricHierarchyFactory" 
interface="org.apache.tapestry.engine.state.StateObjectFactory">
       <invoke-factory>
           <construct 
class="com.cariboonetworks.ads.services.impl.RubricHierarchyFactory">
               <set-configuration property="root" 
configuration-id="RubricRoot"/>
           </construct>
       </invoke-factory>
   </service-point>

   <configuration-point id="RubricRoot">
     <schema>
       <element name="rubric">
         <attribute name="service-id" translator="service-point" 
required="true" unique="true"/>
       </element>
     </schema>
   </configuration-point>
  
   <contribution configuration-id="RubricRoot">
       <rubric service-id="RubricAd"/>
   </contribution>

In the second one, it returns :
"Unable to update property root of 
[EMAIL PROTECTED]: 
argument type mismatch"
and i don't understand why ...

Thanks in advance for any clue.

Stephane