diff --git a/classes/Notice.php b/classes/Notice.php
index 4c831c7cc7..3f138e1cfe 100644
--- a/classes/Notice.php
+++ b/classes/Notice.php
@@ -213,6 +213,28 @@ class Notice extends Managed_DataObject
         return $this->uri;
     }
 
+    /*
+     * Get a Notice object by URI. Will call external plugins for help
+     * using the event StartGetNoticeFromURI.
+     *
+     * @param string $uri A unique identifier for a resource (notice in this case)
+     */
+    static function fromUri($uri)
+    {
+        $notice = null;
+
+        if (Event::handle('StartGetNoticeFromUri', array($uri, &$notice))) {
+            $notice = Notice::getKV('uri', $uri);
+            Event::handle('EndGetNoticeFromUri', array($uri, $notice));
+        }
+
+        if (!$notice instanceof Notice) {
+            throw new UnknownUriException($uri);
+        }
+
+        return $notice;
+    }
+
     /*
      * @param $root boolean If true, link to just the conversation root.
      *
diff --git a/lib/activityobject.php b/lib/activityobject.php
index 505a16e755..2b6105e0d4 100644
--- a/lib/activityobject.php
+++ b/lib/activityobject.php
@@ -440,7 +440,7 @@ class ActivityObject
             $object->type    = (empty($notice->object_type)) ? ActivityObject::NOTE : $notice->object_type;
 
             $object->id      = $notice->uri;
-            $object->title = 'New ' . ActivityObject::canonicalType($object->type) . ' by ';
+            $object->title = 'New ' . self::canonicalType($object->type) . ' by ';
             try {
                 $object->title .= $notice->getProfile()->getAcctUri();
             } catch (ProfileNoAcctUriException $e) {
@@ -584,7 +584,7 @@ class ActivityObject
                 $object->thumbnail = null;
             }
 
-            switch (ActivityObject::canonicalType($object->type)) {
+            switch (self::canonicalType($object->type)) {
             case 'image':
                 $object->largerImage = $file->url;
                 break;
@@ -860,7 +860,7 @@ class ActivityObject
             // We can probably use the whole schema URL here but probably the
             // relative simple name is easier to parse
 
-            $object['objectType'] = ActivityObject::canonicalType($this->type);
+            $object['objectType'] = self::canonicalType($this->type);
 
             // summary
             $object['summary'] = $this->summary;
@@ -945,7 +945,7 @@ class ActivityObject
                 }
             }
 
-            switch (ActivityObject::canonicalType($this->type)) {
+            switch (self::canonicalType($this->type)) {
             case 'image':
                 if (!empty($this->largerImage)) {
                     $object['fullImage'] = array('url' => $this->largerImage);
@@ -964,13 +964,18 @@ class ActivityObject
         return array_filter($object);
     }
 
-    static function canonicalType($type) {
-        $ns = 'http://activitystrea.ms/schema/1.0/';
-        if (substr($type, 0, mb_strlen($ns)) == $ns) {
-            return substr($type, mb_strlen($ns));
-        } else {
-            return $type;
+    public function getIdentifiers() {
+        $ids = array();
+        foreach(array('id', 'link', 'url') as $id) {
+            if (isset($this->$id)) {
+                $ids[] = $this->$id;
+            }
         }
+        return array_unique($ids);
+    }
+
+    static function canonicalType($type) {
+        return ActivityUtils::resolveUri($type, true);
     }
 
     static function mimeTypeToObjectType($mimeType) {
diff --git a/lib/activityutils.php b/lib/activityutils.php
index 8a7039d909..07d8a86141 100644
--- a/lib/activityutils.php
+++ b/lib/activityutils.php
@@ -349,12 +349,57 @@ class ActivityUtils
 
     static function compareTypes($type, $objects)    // this does verbs too!
     {
-        $type = ActivityObject::canonicalType($type);
+        $type = self::resolveUri($type);
         foreach ((array)$objects as $object) {
-            if ($type === ActivityObject::canonicalType($object)) {
+            if ($type === self::resolveUri($object)) {
                 return true;
             }
         }
         return false;
     }
+
+    static function resolveUri($uri, $make_relative=false)
+    {
+        if (empty($uri)) {
+            throw new ServerException('No URI to resolve in ActivityUtils::resolveUri');
+        }
+
+        if (!$make_relative && parse_url($uri, PHP_URL_SCHEME) == '') { // relative -> absolute
+            $uri = Activity::SCHEMA . $uri;
+        } elseif ($make_relative) { // absolute -> relative
+            $uri = basename($uri); //preg_replace('/^http:\/\/activitystrea\.ms\/schema\/1\.0\//', '', $uri);
+        } // absolute schemas pass through unharmed
+
+        return $uri;
+    }
+
+    static function findLocalObject(array $uris, $type=ActivityObject::NOTE) {
+        $object = null;
+        // TODO: Extend this in plugins etc.
+        if (Event::handle('StartFindLocalActivityObject', array($uris, $type, &$object))) {
+            switch (self::resolveUri($type)) {
+            case ActivityObject::PERSON:
+                // GROUP will also be here in due time...
+                $object = new Profile();
+                break;
+            default:
+                $object = new Notice();
+            }
+        }
+        foreach (array_unique($uris) as $uri) {
+            try {
+                // the exception thrown will cancel before reaching $object
+                $object = call_user_func(array($object, 'fromUri'), $uri);
+                break;
+            } catch (Exception $e) {
+                common_debug('Could not find local activity object from uri: '.$uri);
+            }
+        }
+        if (!empty($object)) {
+            Event::handle('EndFindLocalActivityObject', array($object->getUri(), $type, $object));
+        } else {
+            throw new Exception('Could not find any activityobject stored locally with given URI');
+        }
+        return $object;
+    }
 }