diff --git a/Esiur/Data/UUID.cs b/Esiur/Data/UUID.cs
new file mode 100644
index 0000000..ee3dda9
--- /dev/null
+++ b/Esiur/Data/UUID.cs
@@ -0,0 +1,71 @@
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace Esiur.Data
+{
+    [StructLayout(LayoutKind.Sequential, Pack = 1)]
+    public unsafe struct UUID
+    {
+        //4e7db2d8-a785-1b99-1854-4b4018bc5677
+        byte a1;
+        byte a2;
+        byte a3;
+        byte a4;
+        byte b1;
+        byte b2;
+        byte c1;
+        byte c2;
+        byte d1;
+        byte d2;
+        byte e1;
+        byte e2;
+        byte e3;
+        byte e4;
+        byte e5;
+        byte e6;
+
+
+        public UUID(byte[] data)
+        {
+            if (data.Length < 16)
+                throw new Exception("UUID data size must be at least 16 bytes");
+
+            for(var i = 0; i < 16; i++)
+                Data[i] = data[i];
+        }
+
+        public override string ToString()
+        {
+            return $"{a1.ToString("x2")}{a2.ToString("x2")}{a3.ToString("x2")}{a4.ToString("x2")}-{b1.ToString("x2")}{b2.ToString("x2")}-{c1.ToString("x2")}{c2.ToString("x2")}-{d1.ToString("x2")}{d2.ToString("x2")}-{e1.ToString("x2")}{e2.ToString("x2")}{e3.ToString("x2")}{e4.ToString("x2")}{e5.ToString("x2")}{e6.ToString("x2")}";
+        }
+
+        public static bool operator == (UUID a, UUID b)
+        {
+            return a.a1 == b.a1
+                    && a.a2 == b.a2
+                    && a.a3 == b.a3
+                    && a.a4 == b.a4
+                    && a.b1 == b.b1
+                    && a.b2 == b.b2
+                    && a.c1 == b.c1
+                    && a.c2 == b.c2
+                    && a.d1 == b.d1
+                    && a.d2 == b.d2
+                    && a.e1 == b.e1
+                    && a.e2 == b.e2
+                    && a.e3 == b.e3
+                    && a.e4 == b.e4
+                    && a.e5 == b.e5
+                    && a.e6 == b.e6;
+        }
+
+        public static bool operator !=(UUID a, UUID b)
+        {
+            return !(a == b);
+        }
+
+    }
+}
diff --git a/Esiur/Resource/Template/TypeTemplate.cs b/Esiur/Resource/Template/TypeTemplate.cs
index 67f4cfb..82b2e4f 100644
--- a/Esiur/Resource/Template/TypeTemplate.cs
+++ b/Esiur/Resource/Template/TypeTemplate.cs
@@ -167,6 +167,9 @@ public class TypeTemplate
 
         var tn = Encoding.UTF8.GetBytes(GetTypeClassName(type));
         var hash = SHA256.Create().ComputeHash(tn).Clip(0, 16);
+        hash[6] = (byte)((hash[6] & 0xF) | 0x80);
+        hash[8] = (byte)((hash[8] & 0xF) | 0x80);
+
         var rt = new Guid(hash);
         return rt;
     }
diff --git a/Test/Program.cs b/Test/Program.cs
index a3a67e7..a56063e 100644
--- a/Test/Program.cs
+++ b/Test/Program.cs
@@ -55,18 +55,45 @@ namespace Test
 
     class Program
     {
-        static async Task Main(string[] args)
+
+        static void TestSerialization(object x)
         {
 
-
-            var x = new uint[] {1,2};// new byte[1024];
-            // var rr = DC.ToHex(Codec.Compose(aa, null));
             var y = Codec.Compose(x, null);
             var rr = DC.ToHex(y);
 
-            Console.WriteLine(rr);
+            Console.WriteLine(x.GetType().Name + ": " + rr);
+        }
+
+
+        [Export]
+        public class StudentRecord:IRecord
+        {
+            public string Name { get; set; }
+            public byte Grade { get; set; }
+        }
+
+        static async Task Main(string[] args)
+        {
+
+            TestSerialization(new Map<string, byte?>
+            {
+                ["C++"] = 1,
+                ["C#"] = 2,
+                ["JS"] = null
+            });
+
+            TestSerialization(new StudentRecord() { Name = "Ali", Grade = 90});
+
+            var tn = Encoding.UTF8.GetBytes("MyProject.Tools.Logging.LogRecord");
+            var hash = System.Security.Cryptography.SHA256.Create().ComputeHash(tn).Clip(0, 16);
+            hash[6] = (byte)((hash[6] & 0xF) | 0x80);
+            hash[8] = (byte)((hash[8] & 0xF) | 0x80);
+
+            var g = new Guid(hash);
+
+            Console.WriteLine(g);
 
-            var rp = RepresentationType.FromType(x.GetType());
 
             var hhhh = Warehouse.GetTemplateByType(typeof(IMyRecord));