diff -r 000000000000 -r a0f15cb8c730 chat/shared/src/main/java/org/apidesign/demo/chat/shared/MessageImpl.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/chat/shared/src/main/java/org/apidesign/demo/chat/shared/MessageImpl.java	Fri Apr 22 05:56:47 2016 +0200
@@ -0,0 +1,59 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (C) 2013 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package org.apidesign.demo.chat.shared;
+
+import net.java.html.json.ComputedProperty;
+import net.java.html.json.Model;
+import net.java.html.json.Property;
+
+/** Generic model of communication between browser and a chat server.
+ * The same code is then used on the server, on the client and even in unit 
+ * tests.
+ * 
+ * @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>
+ */
+@Model(className = "Message", properties = {
+    @Property(name = "user", type = String.class),
+    @Property(name = "comment", type = String.class),
+    @Property(name = "since", type = long.class)    
+})
+class MessageImpl {
+    @ComputedProperty static String at(long since) {
+        long delta = since / 1000;
+        if (delta <= 0) {
+            return "Boot-time";
+        }
+        if (delta < 60) {
+            return delta + "s";
+        }
+        delta /= 60;
+        return delta + "min";
+    }
+
+    @Model(className = "Query", properties = {
+        @Property(name = "messages", type = Message.class, array = true)
+    })
+    class QryMsgs {
+    }
+}