+ const READ = ActivityNamespace::ACTIVITY2 . 'Read';
+ /**
+ * Indicates that the actor has listened to the object.
+ *
+ * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-listen
+ * @var string
+ */
+ const LISTEN = ActivityNamespace::ACTIVITY2 . 'Listen';
+ /**
+ * Indicates that the actor has viewed the object.
+ *
+ * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-view
+ * @var string
+ */
+ const VIEW = ActivityNamespace::ACTIVITY2 . 'View';