diff --git a/src/main/clj/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2.clj b/src/main/clj/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2.clj
index e06a7b5..d0dbda5 100644
--- a/src/main/clj/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2.clj
+++ b/src/main/clj/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2.clj
@@ -36,11 +36,17 @@
 
 ;http://www.w3.org/ns/activitystreams#id
 ;TODO: how do we translate this? rdfs:domain [a owl:Class ;    owl:unionOf (as:Link as:Object)]
+;TODO evtl sind ::owl/FunctionalProperty, ::owl/DatatypeProperty, ::owl/DeprecatedProperty nur meta informationen?
 (s/def ::id (s/and ::owl/FunctionalProperty
                    ::owl/DatatypeProperty
                    ::owl/DeprecatedProperty
                    core/uri-string?))
 
+;TODO: we will need such a predicate ...
+;(defn-spec isFunctional? bool?
+;  [spec keyword?]
+;  (search-in-meta spec))
+
 ; TODO: type can have multiple values!! Affects also the fct match-type and all specs that uses it!
 (s/def ::type #(or (core/uri-string? %) (contains? objectAndLinkTypes %)))