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 d74ac6d..b410ecc 100644
--- a/src/main/clj/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2.clj
+++ b/src/main/clj/org/domaindrivenarchitecture/activity_pub_poc/activitystreams2.clj
@@ -2,17 +2,36 @@
   (:require [clojure.spec.alpha :as s]
             [org.domaindrivenarchitecture.activity-pub-poc.core :as core]))
 
+; TODO: We could do these with multispec, but that is too much for a POC
+(def objectAndLinkTypes #{; Object Types
+                         "Article"
+                         "Audio"
+                         "Document"
+                         "Event"
+                         "Image"
+                         "Note"
+                         "Page"
+                         "Place"
+                         "Profile"
+                         "Relationship"
+                         "Tombstone"
+                         "Video"
+                         ; Link Types
+                         "Mention"})
+
 (s/def ::Object (s/or
                  :uri core/uri-string?
-                 :map (s/keys
-                       :req-un [::id ::type] ;type darf nicht "Link" sein
-                       :opt-un [::attributedTo ::und-mehr])))
+                 :map (s/and (s/keys
+                              :req-un [::id ::type]
+                              :opt-un [::attributedTo ::und-mehr])
+                             #(not (= (:type %) "Link")))))
 (s/def ::id core/uri-string?)
-(s/def ::type #(or (core/uri-string? %) (= % "Link")))
+(s/def ::type #(or (core/uri-string? %) (contains? objectAndLinkTypes %)))
 
-(s/def ::Link (s/keys
-               :req-un [::type] ; type muss "Link" sein
-               :opt-un [::attributedTo ::und-mehr]))
+(s/def ::Link (s/and (s/keys
+                      :req-un [::type]
+                      :opt-un [::attributedTo ::und-mehr])
+                     #(= (:type %) "Link")))
 
 (s/def ::Relationship (s/keys :req-un [::object ::und-mehr]))
 
@@ -56,4 +75,21 @@
   {:id "https://social.bla/alyssa#likes/RANDOMHASH",
    :type "Like",
    :actor "https://social.bla/alyssa",
-   :object "https://chatty.bla/ben/posts/234s23-2g34234-2hhj536"})
\ No newline at end of file
+   :object "https://chatty.bla/ben/posts/234s23-2g34234-2hhj536"})
+
+(def testLink
+  {:context "https://www.w3.org/ns/activitystreams",
+   :type "Link",
+   :href "http://example.org/abc",
+   :hreflang "en",
+   :mediaType "text/html",
+   :name "An example link"})
+
+(def testObject
+  {:context "https://www.w3.org/ns/activitystreams",
+   :type "Note",
+   :id "https://social.bla/alyssa",
+   :href "http://example.org/abc",
+   :hreflang "en",
+   :mediaType "text/html",
+   :name "An example object"})
\ No newline at end of file