diff --git a/Ooui/Element.cs b/Ooui/Element.cs
index 31da35a..0155daf 100644
--- a/Ooui/Element.cs
+++ b/Ooui/Element.cs
@@ -1,20 +1,71 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 
 namespace Ooui
 {
     public class Element
     {
-        public string Id { get; private set; }
+        public string Id { get; private set; } = GenerateId ();
+
+        public HtmlMapping Mapping { get; private set; }
+
+        readonly List<Message> messages = new List<Message> ();
+        readonly List<Message> stateMessages = new List<Message> ();
 
         public Element ()
         {
-            Id = GenerateId ();
+            Mapping = HtmlMapping.Get (GetType ());
+            LogCreate ();
         }
 
-        protected bool SetProperty<T> (ref T backingStore, T newValue)
+        protected void Log (Message message)
+        {
+            messages.Add (message);
+
+            switch (message.MessageType) {
+                case MessageType.Create:
+                    stateMessages.Add (message);
+                    break;
+                case MessageType.SetProperty:
+                    {
+                        var old = stateMessages.FirstOrDefault (
+                            x => x.MessageType == MessageType.SetProperty &&
+                                x.Member == message.Member);
+                        if (old != null) {
+                            stateMessages.Remove (old);
+                        }
+                        stateMessages.Add (message);
+                    }
+                    break;
+            }
+        }
+
+        protected void LogCreate ()
+        {
+            Log (new Message {
+                MessageType = MessageType.Create,
+                TargetId = Id,
+                Value = Mapping.TagName,
+            });
+        }
+
+        protected void LogSetProperty (string propertyName, object value)
+        {
+            var m = new Message {
+                MessageType = MessageType.SetProperty,
+                TargetId = Id,
+                Member = Mapping.GetMemberPath (propertyName),
+            };
+            m.SetValue (value);
+            Log (m);
+        }
+
+        protected bool SetProperty<T> (ref T backingStore, T newValue, string propertyName = "")
         {
             if (!backingStore.Equals (newValue)) {
                 backingStore = newValue;
+                LogSetProperty (propertyName, newValue);
                 return true;
             }
             return false;
diff --git a/Ooui/HtmlMapping.cs b/Ooui/HtmlMapping.cs
new file mode 100644
index 0000000..c98fb03
--- /dev/null
+++ b/Ooui/HtmlMapping.cs
@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+
+namespace Ooui
+{
+    public class HtmlMapping
+    {
+        readonly Type type;
+        public string TagName { get; private set; }
+
+        public HtmlMapping (Type type)
+        {
+            this.type = type;
+            TagName = type.Name.ToLowerInvariant ();
+        }
+
+        public string GetMemberPath (string propertyName)
+        {
+            return propertyName;
+        }
+
+        static readonly Dictionary<string, HtmlMapping> mappings =
+            new Dictionary<string, HtmlMapping> ();
+
+        public static HtmlMapping Get (Type type)
+        {
+            var key = type.FullName;
+            HtmlMapping m;
+            if (!mappings.TryGetValue (key, out m)) {
+                m = new HtmlMapping (type);
+                mappings[key] = m;
+            }
+            return m;
+        }
+    }
+}
diff --git a/Ooui/Message.cs b/Ooui/Message.cs
new file mode 100644
index 0000000..fcde6c0
--- /dev/null
+++ b/Ooui/Message.cs
@@ -0,0 +1,49 @@
+using System;
+
+namespace Ooui
+{
+    public class Message
+    {
+        public DateTime CreatedTime = DateTime.UtcNow;
+        public MessageType MessageType = MessageType.Nop;
+        public string TargetId = "";
+        public string Member = "";
+        public string Value = "";
+
+        public void SetValue (object value)
+        {
+            switch (value) {
+                case null:
+                    Value = "null";
+                    break;
+                case String s:
+                    Value = EncodeString (s);
+                    break;
+                default:
+                    Value = String.Format (System.Globalization.CultureInfo.InvariantCulture, "{0}", value);
+                    break;
+            }
+        }
+
+        public static string EncodeString (string s)
+        {
+            return s;
+        }
+        public static string DecodeString (string s)
+        {
+            return s;
+        }
+    }
+
+    public enum MessageType
+    {
+        Nop,
+        Create,
+        SetProperty,
+    }
+
+    public enum ValueType
+    {
+        String
+    }
+}