double import :)

 # baseURI: http://data.posccaesar.org/ilap/userfields/
+# imports: http://data.posccaesar.org/ilap/
 
 # c14n-version: 3
 @prefix : <http://data.posccaesar.org/ilap/userfields/> .
@@ -17,6 +18,7 @@ ilap:shouldUseAnyUri
 .
 :
   rdf:type owl:Ontology ;
+  owl:imports ilap: ;
 .
 :SourceSpecifiedUserField
   rdf:type owl:Class ;
@@ -613,12 +615,6 @@ ilap:shouldUseAnyUri
       rdf:type owl:Restriction ;
       owl:maxQualifiedCardinality "1"^^xsd:nonNegativeInteger ;
       owl:onClass ilap:FreeFieldValue ;
-      owl:onProperty :hasMainWorkCenter ;
-    ] ;
-  rdfs:subClassOf [
-      rdf:type owl:Restriction ;
-      owl:maxQualifiedCardinality "1"^^xsd:nonNegativeInteger ;
-      owl:onClass ilap:FreeFieldValue ;
       owl:onProperty :hasMainWorkCenterPlant ;
     ] ;
   rdfs:subClassOf [
@@ -681,6 +677,12 @@ ilap:shouldUseAnyUri
       owl:onClass ilap:FreeFieldValue ;
       owl:onProperty :hasSuperiorPSnetworkActivity ;
     ] ;
+  rdfs:subClassOf [
+      rdf:type owl:Restriction ;
+      owl:maxQualifiedCardinality "1"^^xsd:nonNegativeInteger ;
+      owl:onClass ilap:MainWorkCenter ;
+      owl:onProperty :hasMainWorkCenter ;
+    ] ;
 .
 :SpecifiedUserField_1
   rdf:type :SpecifiedUserField ;