diff -r 3d16ad54b3dc -r 0a658e53177c src/main/java/de/uapcore/lightpit/Constants.java
--- a/src/main/java/de/uapcore/lightpit/Constants.java	Sat May 30 18:12:38 2020 +0200
+++ b/src/main/java/de/uapcore/lightpit/Constants.java	Mon Jun 01 14:46:58 2020 +0200
@@ -92,6 +92,11 @@
     public static final String REQ_ATTR_CONTENT_PAGE = fqn(AbstractLightPITServlet.class, "content-page");
 
     /**
+     * Key for the view model object (the type depends on the rendered site).
+     */
+    public static final String REQ_ATTR_VIEWMODEL = "viewmodel";
+
+    /**
      * Key for the name of the additional stylesheet used by a module.
      */
     public static final String REQ_ATTR_STYLESHEET = fqn(AbstractLightPITServlet.class, "extraCss");