diff --git a/lib/ontologies_linked_data/concerns/ontology_submissions/submission_metadata_extractor.rb b/lib/ontologies_linked_data/concerns/ontology_submissions/submission_metadata_extractor.rb
index 63744af6..229b4630 100644
--- a/lib/ontologies_linked_data/concerns/ontology_submissions/submission_metadata_extractor.rb
+++ b/lib/ontologies_linked_data/concerns/ontology_submissions/submission_metadata_extractor.rb
@@ -8,7 +8,7 @@ def extract_metadata
           ontology_iri = extract_ontology_iri
 
           self.version = version_info if version_info
-          self.uri = ontology_iri if ontology_iri
+          self.uri = RDF::URI.new(ontology_iri) if ontology_iri
 
         end
 
diff --git a/lib/ontologies_linked_data/models/ontology_submission.rb b/lib/ontologies_linked_data/models/ontology_submission.rb
index 075d218f..82990c03 100644
--- a/lib/ontologies_linked_data/models/ontology_submission.rb
+++ b/lib/ontologies_linked_data/models/ontology_submission.rb
@@ -15,6 +15,7 @@ class OntologySubmission < LinkedData::Models::Base
       include LinkedData::Concerns::SubmissionProcessable
       include LinkedData::Concerns::OntologySubmission::MetadataExtractor
       include LinkedData::Concerns::OntologySubmission::Validators
+      extend LinkedData::Concerns::OntologySubmission::DefaultCallbacks
 
       FLAT_ROOTS_LIMIT = 1000
 
@@ -38,10 +39,10 @@ class OntologySubmission < LinkedData::Models::Base
 
       # Ontology metadata
       # General metadata
-      attribute :URI, namespace: :omv, type: :uri, enforce: %i[existence distinct_of_identifier], fuzzy_search: true
+      attribute :uri, namespace: :omv, type: :uri, enforce: %i[distinct_of_identifier], fuzzy_search: true
       attribute :versionIRI, namespace: :owl, type: :uri, enforce: [:distinct_of_URI]
       attribute :version, namespace: :omv
-      attribute :status, namespace: :omv, enforce: %i[existence], default: ->(x) { 'production' }
+      attribute :status, namespace: :omv, default: ->(x) { 'production' }
       attribute :deprecated, namespace: :owl, type: :boolean, default: ->(x) { false }
       attribute :hasOntologyLanguage, namespace: :omv, type: :ontology_format, enforce: [:existence]
       attribute :hasFormalityLevel, namespace: :omv, type: :uri
@@ -51,7 +52,7 @@ class OntologySubmission < LinkedData::Models::Base
       attribute :identifier, namespace: :dct, type: %i[list uri], enforce: [:distinct_of_URI]
 
       # Description metadata
-      attribute :description, namespace: :omv, enforce: %i[concatenate existence], fuzzy_search: true
+      attribute :description, namespace: :omv, enforce: %i[concatenate], fuzzy_search: true
       attribute :homepage, namespace: :foaf, type: :uri
       attribute :documentation, namespace: :omv, type: :uri
       attribute :notes, namespace: :omv, type: :list