Explain the bytes associated with the NFC type 4 tag.

Change-Id: Ibe12a8cb94032f52e02ef28a423203483b1e096f
diff --git a/apps/Tag/src/com/android/apps/tag/TagDBHelper.java b/apps/Tag/src/com/android/apps/tag/TagDBHelper.java
index 5739da9..6209507 100644
--- a/apps/Tag/src/com/android/apps/tag/TagDBHelper.java
+++ b/apps/Tag/src/com/android/apps/tag/TagDBHelper.java
@@ -46,55 +46,72 @@
     private static final String INSERT =
             "INSERT INTO NdefMessage (bytes, date, saved) values (?, ?, ?)";
 
+    /**
+     * A real NFC tag containing an NFC "smart poster".  This smart poster
+     * consists of the text "NFC Forum Type 4 Tag" in english combined with
+     * the URL "http://www.nxp.com/nfc"
+     */
     private static final byte[] REAL_NFC_MSG = new byte[] {
-            (byte) 0xd1,
-            (byte) 0x02,
-            (byte) 0x2b,
-            (byte) 0x53,
-            (byte) 0x70,
-            (byte) 0x91,
-            (byte) 0x01,
-            (byte) 0x17,
-            (byte) 0x54,
-            (byte) 0x02,
-            (byte) 0x65,
-            (byte) 0x6e,
-            (byte) 0x4e,
-            (byte) 0x46,
-            (byte) 0x43,
-            (byte) 0x20,
-            (byte) 0x46,
-            (byte) 0x6f,
-            (byte) 0x72,
-            (byte) 0x75,
-            (byte) 0x6d,
-            (byte) 0x20,
-            (byte) 0x54,
-            (byte) 0x79,
-            (byte) 0x70,
-            (byte) 0x65,
-            (byte) 0x20,
-            (byte) 0x34,
-            (byte) 0x20,
-            (byte) 0x54,
-            (byte) 0x61,
-            (byte) 0x67,
-            (byte) 0x51,
-            (byte) 0x01,
-            (byte) 0x0c,
-            (byte) 0x55,
-            (byte) 0x01,
-            (byte) 0x6e,
-            (byte) 0x78,
-            (byte) 0x70,
-            (byte) 0x2e,
-            (byte) 0x63,
-            (byte) 0x6f,
-            (byte) 0x6d,
-            (byte) 0x2f,
-            (byte) 0x6e,
-            (byte) 0x66,
-            (byte) 0x63
+            (byte) 0xd1,                   // MB=1 ME=1 CF=0 SR=1 IL=0 TNF=001
+            (byte) 0x02,                   // Type Length = 2
+            (byte) 0x2b,                   // Payload Length = 43
+            (byte) 0x53, (byte) 0x70,      // Type = {'S', 'p'} (smart poster)
+
+            // begin smart poster payload
+            // begin smart poster record #1
+            (byte) 0x91,                   // MB=1 ME=0 CF=0 SR=1 IL=0 TNF=001
+            (byte) 0x01,                   // Type Length = 1
+            (byte) 0x17,                   // Payload Length = 23
+            (byte) 0x54,                   // Type = {'T'} (Text data)
+            (byte) 0x02,                   // UTF-8 encoding, language code length = 2
+            (byte) 0x65, (byte) 0x6e,      // language = {'e', 'n'} (english)
+
+            // Begin text data within smart poster record #1
+            (byte) 0x4e,                   // 'N'
+            (byte) 0x46,                   // 'F'
+            (byte) 0x43,                   // 'C'
+            (byte) 0x20,                   // ' '
+            (byte) 0x46,                   // 'F'
+            (byte) 0x6f,                   // 'o'
+            (byte) 0x72,                   // 'r'
+            (byte) 0x75,                   // 'u'
+            (byte) 0x6d,                   // 'm'
+            (byte) 0x20,                   // ' '
+            (byte) 0x54,                   // 'T'
+            (byte) 0x79,                   // 'y'
+            (byte) 0x70,                   // 'p'
+            (byte) 0x65,                   // 'e'
+            (byte) 0x20,                   // ' '
+            (byte) 0x34,                   // '4'
+            (byte) 0x20,                   // ' '
+            (byte) 0x54,                   // 'T'
+            (byte) 0x61,                   // 'a'
+            (byte) 0x67,                   // 'g'
+            // end Text data within smart poster record #1
+            // end smart poster record #1
+
+            // begin smart poster record #2
+            (byte) 0x51,                   // MB=0 ME=1 CF=0 SR=1 IL=0 TNF=001
+            (byte) 0x01,                   // Type Length = 1
+            (byte) 0x0c,                   // Payload Length = 12
+            (byte) 0x55,                   // Type = { 'U' } (URI)
+
+            // begin URI data within smart poster record #2
+            (byte) 0x01,                   // URI Prefix = 1 ("http://www.")
+            (byte) 0x6e,                   // 'n'
+            (byte) 0x78,                   // 'x'
+            (byte) 0x70,                   // 'p'
+            (byte) 0x2e,                   // '.'
+            (byte) 0x63,                   // 'c'
+            (byte) 0x6f,                   // 'o'
+            (byte) 0x6d,                   // 'm'
+            (byte) 0x2f,                   // '/'
+            (byte) 0x6e,                   // 'n'
+            (byte) 0x66,                   // 'f'
+            (byte) 0x63                    // 'c'
+            // end URI data within smart poster record #2
+            // end smart poster record #2
+            // end smart poster payload
     };
 
     public TagDBHelper(Context context) {