diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 4f6aeea..3ccc7cf 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -20,6 +20,9 @@ jobs:
       - name: test for ERRORs with ROBOT report
         run: |
           robot report --profile .github/report_profile.txt --input dfgfo.ttl
+      - name: validate ontology against OWL DL profile
+        run: |
+          robot validate-profile --profile DL --input dfgfo.ttl
       - name: produce report
         run: |
           robot report --profile .github/report_profile.txt --input dfgfo.ttl --output report.txt
diff --git a/README.md b/README.md
index 559bcca..c9a207a 100644
--- a/README.md
+++ b/README.md
@@ -46,7 +46,7 @@ Run script to create ontologu `python scripts/create_ontology.py`
 ## Ontology contributions:
 Contributions are welcome.
 
-At every push or pull_request a [ROBOT report](http://robot.obolibrary.org/report) test will be run from [.github/workflows/main.yml](.github/workflows/main.yml).
+At every push or pull_request a [ROBOT report](http://robot.obolibrary.org/report) and  [ROBOT validate OWL DL profile](http://robot.obolibrary.org/validate-profile)test will be run from [.github/workflows/main.yml](.github/workflows/main.yml).
 
 
 
diff --git a/dfgfo.ttl b/dfgfo.ttl
index b399969..046b5db 100644
--- a/dfgfo.ttl
+++ b/dfgfo.ttl
@@ -4,6 +4,14 @@
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix terms: <http://purl.org/dc/terms/> .
 
+dc:creator a owl:AnnotationProperty .
+
+dc:description a owl:AnnotationProperty .
+
+dc:title a owl:AnnotationProperty .
+
+terms:license a owl:AnnotationProperty .
+
 <https://github.com/tibonto/dfgfo> a owl:Ontology ;
     dc:creator "André Castro",
         "Deutsche Forschungsgemeinschaft (DFG)",
@@ -11,7 +19,7 @@
     dc:description "DFG Fachsystematik Ontology / DFG Classification of Subject Areas Ontology (DFGFO) encodes the DFG Classification of Subject Areas into an ontology, where each subject number are is enconded into a Class with subclass statements following the DFG Classification of Subject Areas hierarchy. Labels are provide German and English." ;
     dc:title "DFG Classification of Subject Areas Ontology"@en ;
     terms:license <https://creativecommons.org/licenses/by/4.0/> ;
-    <http://www.w3.org/2000/01/rdf-schema#comment:> "DFG Classification of Subject Areas Ontology is being created as part of the TIB Terminology Service" .
+    rdfs:comment "DFG Classification of Subject Areas Ontology is being created as part of the TIB Terminology Service" .
 
 dfgfo:101-01 a owl:Class ;
     rdfs:label "Ur- und Frühgeschichte (weltweit)"@de,
diff --git a/metadata.ttl b/metadata.ttl
index 1ce1d70..c758f4e 100644
--- a/metadata.ttl
+++ b/metadata.ttl
@@ -5,12 +5,21 @@
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix obo: <http://purl.obolibrary.org/obo/> .
 
+
+dc:creator rdf:type owl:AnnotationProperty .
+
+dc:description rdf:type owl:AnnotationProperty .
+
+dc:title rdf:type owl:AnnotationProperty .
+
+terms:license rdf:type owl:AnnotationProperty .
+
 <https://github.com/tibonto/dfgfo> rdf:type owl:Ontology ;
                                    dc:creator "Deutsche Forschungsgemeinschaft (DFG)",
                                               "André Castro",
                                               "Susanne Arndt";
                                    dc:description "DFG Fachsystematik Ontology / DFG Classification of Subject Areas Ontology (DFGFO) encodes the DFG Classification of Subject Areas into an ontology, where each subject number are is enconded into a Class with subclass statements following the DFG Classification of Subject Areas hierarchy. Labels are provide German and English.";
                                    dc:title "DFG Classification of Subject Areas Ontology"@en ;
-                                   rdfs:comment: "DFG Classification of Subject Areas Ontology is being created as part of the TIB Terminology Service" ;
+                                   rdfs:comment "DFG Classification of Subject Areas Ontology is being created as part of the TIB Terminology Service" ;
                                    terms:license <https://creativecommons.org/licenses/by/4.0/> . 
 # TODO: provide appropriate license - same license should go to github repo