diff --git a/.travis.yml b/.travis.yml
index 712c45c..49d023f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,12 +7,6 @@ cache:
 
 matrix:
   include:
-      - php: 5.3
-        dist: precise
-      - php: 5.4
-        dist: precise
-      - php: 5.5
-        dist: precise
       - php: 5.6
       - php: 7.0
       - php: 7.1
diff --git a/ActivityRepositoryInterface.php b/ActivityRepositoryInterface.php
new file mode 100644
index 0000000..4d23d57
--- /dev/null
+++ b/ActivityRepositoryInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace XApi\Repository\Api;
+
+use Xabbuh\XApi\Common\Exception\NotFoundException;
+use Xabbuh\XApi\Model\Activity;
+use Xabbuh\XApi\Model\IRI;
+
+/**
+ * Public API of an Experience API (xAPI) {@link Activity} repository.
+ *
+ * @author Jérôme Parmentier <jerome.parmentier@acensi.fr>
+ */
+interface ActivityRepositoryInterface
+{
+    /**
+     * Finds an {@link Activity} by id.
+     *
+     * @param IRI $activityId The activity id to filter by
+     *
+     * @return Activity The activity
+     *
+     * @throws NotFoundException if no Activity with the given IRI does exist
+     */
+    public function findActivityById(IRI $activityId);
+}
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b23c1f5..dce26dc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,18 @@
 CHANGELOG
 =========
 
+0.4.0
+-----
+
+* dropped suppport for PHP < 5.6 and HHVM
+
+* made the package compatible with `3.x` releases of `ramsey/uuid`
+
+* allow `2.x` and `3.x` releases of the `php-xapi/model` package too
+
+* added an `ActivityRepositoryInterface` that defines the public API of
+  an activity repository
+
 0.3.1
 -----
 
diff --git a/Test/Functional/ActivityRepositoryTest.php b/Test/Functional/ActivityRepositoryTest.php
new file mode 100644
index 0000000..29cdaac
--- /dev/null
+++ b/Test/Functional/ActivityRepositoryTest.php
@@ -0,0 +1,76 @@
+<?php
+
+/*
+ * This file is part of the xAPI package.
+ *
+ * (c) Christian Flothmann <christian.flothmann@xabbuh.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace XApi\Repository\Api\Test\Functional;
+
+use PHPUnit\Framework\TestCase;
+use Xabbuh\XApi\Model\Activity;
+use Xabbuh\XApi\Model\IRI;
+use XApi\Repository\Api\ActivityRepositoryInterface;
+
+/**
+ * @author Jérôme Parmentier <jerome.parmentier@acensi.fr>
+ */
+abstract class ActivityRepositoryTest extends TestCase
+{
+    /**
+     * @var ActivityRepositoryInterface
+     */
+    private $activityRepository;
+
+    protected function setUp()
+    {
+        $this->activityRepository = $this->createActivityRepository();
+        $this->cleanDatabase();
+    }
+
+    protected function tearDown()
+    {
+        $this->cleanDatabase();
+    }
+
+    /**
+     * @expectedException \Xabbuh\XApi\Common\Exception\NotFoundException
+     */
+    public function testFetchingNonExistingActivityThrowsException()
+    {
+        $this->activityRepository->findActivityById(IRI::fromString('not-existing'));
+    }
+
+    /**
+     * @dataProvider getStatementsWithId
+     */
+    public function testActivitiesCanBeRetrievedById(Activity $activity)
+    {
+        $fetchedActivity = $this->activityRepository->findActivityById($activity->getId());
+
+        $this->assertTrue($activity->equals($fetchedActivity));
+    }
+
+    public function getActivitiesWithId()
+    {
+        $fixtures = array();
+
+        foreach (get_class_methods('Xabbuh\XApi\DataFixtures\ActivityFixtures') as $method) {
+            $activity = call_user_func(array('Xabbuh\XApi\DataFixtures\ActivityFixtures', $method));
+
+            if ($activity instanceof Activity) {
+                $fixtures[$method] = array($activity);
+            }
+        }
+
+        return $fixtures;
+    }
+
+    abstract protected function createActivityRepository();
+
+    abstract protected function cleanDatabase();
+}
diff --git a/composer.json b/composer.json
index 99457f9..60c0f62 100644
--- a/composer.json
+++ b/composer.json
@@ -11,10 +11,12 @@
         }
     ],
     "require": {
+        "php": "^5.6 || ^7.0",
         "ramsey/uuid": "^2.8 || ^3.0",
-        "php-xapi/model": "^1.0",
+        "php-xapi/model": "^1.1 || ^2.0 || ^3.0",
         "php-xapi/test-fixtures": "^1.0"
     },
+    "minimum-stability": "dev",
     "conflict": {
         "xabbuh/xapi-storage-api": "*"
     },
@@ -25,7 +27,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "0.3.x-dev"
+            "dev-master": "0.4.x-dev"
         }
     }
 }