diff --git a/PPEO.owl b/PPEO.owl
index 99a0456..84d5f60 100644
--- a/PPEO.owl
+++ b/PPEO.owl
@@ -1416,6 +1416,13 @@
                 </owl:onDataRange>
             </owl:Restriction>
         </rdfs:subClassOf>
+        <rdfs:subClassOf>
+            <owl:Restriction>
+                <owl:onProperty rdf:resource="http://purl.org/ppeo/PPEO.owl#hasDescription"/>
+                <owl:maxQualifiedCardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#nonNegativeInteger">1</owl:maxQualifiedCardinality>
+                <owl:onDataRange rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
+            </owl:Restriction>
+        </rdfs:subClassOf>
         <rdfs:comment xml:lang="en">A parameter of the environment which is represented by a name and a value.</rdfs:comment>
         <rdfs:label xml:lang="en">environment parameter</rdfs:label>
     </owl:Class>
@@ -2766,4 +2773,4 @@ It is recommended that a Study have a description.</rdfs:comment>
         <hasType rdf:datatype="http://www.w3.org/2001/XMLSchema#string">z (m)</hasType>
         <rdfs:comment xml:lang="en">The local spatial coordinate z (in meters)</rdfs:comment>
     </owl:NamedIndividual>
-</rdf:RDF>
\ No newline at end of file
+</rdf:RDF>