diff --git a/coos.html b/coos.html
index 7c82f9a..aefd1fd 100644
--- a/coos.html
+++ b/coos.html
@@ -733,7 +733,7 @@ <h2>Products</h2>
 				<li><code>content</code> can be “Data”, “Metadata”, “Analysis” or “Model”</li>
 				<li><code>presentation</code> can be “Dataset”, “Publication”, “Viualization”, “Infographic”, “Thematic Map” or “Interactive”</li>
 			</ul>
-			<p>Implementors can define additional instances of the <code>coos:ProductContent</code> of <code>coos:ProductPresentation</code> for their specific needs.</p>
+			<p>Implementors can define additional instances of <code>coos:ProductContent</code> or <code>coos:ProductPresentation</code> for their specific needs.</p>
 
 		</section>
 
diff --git a/coos.ttl b/coos.ttl
index eecbe47..8a444f5 100644
--- a/coos.ttl
+++ b/coos.ttl
@@ -21,6 +21,7 @@
 #################################################################
 
 <http://id.unece.org/def/coos> a owl:Ontology, voaf:Vocabulary ;
+    owl:imports <http://www.w3.org/2004/02/skos/core> ;
     dc:title "COOS: a core ontology for Official Statistics"@en , "COOS : une ontologie centrale pour la Statistique Officielle"@fr , "COOS: Una ontología básica para las Estadísticas Oficiales"@es ;
     dc:contributor "Guillaume Duffes" , "Dan Gillman" , "Flavio Rizzolo" , "Francine Kalonji", "Juan Muñoz" , "Florian Vucko" , "Thomas Francart" ;
     dc:creator "Franck Cotton" ;
@@ -237,20 +238,24 @@ coos:ProductPresentation a owl:Class , rdfs:Class ;
     rdfs:seeAlso coos:productPresentations ;
     skos:prefLabel "Product presentation"@en , "Presentación del producto"@es , "Présentation de produit"@fr ;
     rdfs:isDefinedBy <http://id.unece.org/def/coos> ;
-    owl:equivalentClass [
-	a owl:Class ;
-	owl:oneOf ( coos:datasetPresentation coos:publicationPresentation coos:viualizationPresentation coos:infographicPresentation coos:thematicMapPresentation coos:interactivePresentation )
-    ] .
+    owl:equivalentClass [ 
+        rdf:type owl:Restriction ;
+        owl:onProperty skos:inScheme ;
+        owl:hasValue coos:productPresentations
+    ]
+.
 
 coos:ProductContent a owl:Class , rdfs:Class ;
     rdfs:subClassOf skos:Concept ;
     rdfs:seeAlso coos:productContents ;
     skos:prefLabel "Product content"@en , "Contenido del producto"@es , "Contenu de produit"@fr ;
     rdfs:isDefinedBy <http://id.unece.org/def/coos> ;
-    owl:equivalentClass [
-	a owl:Class ;
-	owl:oneOf ( coos:dataContent coos:metadataContent coos:analysisContent coos:modelContent )
-    ] .
+    owl:equivalentClass [ 
+        rdf:type owl:Restriction ;
+        owl:onProperty skos:inScheme ;
+        owl:hasValue coos:productContents
+    ]
+.
 
 
 # Classes related to the 'organizations' domain