diff --git a/README.md b/README.md
index e25763a7a..ecd909eda 100644
--- a/README.md
+++ b/README.md
@@ -38,22 +38,74 @@ value, such as 3400.
 
 Signals are organized into a tree such as outlined below.
 
-![Signal tree](https://github.com/PDXostc/vehicle_signal_interface/raw/master/pics/tree.png)
+![Signal tree](pics/tree.png)<br>
+*Fig 1. A signal tree example*
+
+## SIGNAL TYPE
+Each signal specifies a type from the following set (from FrancaIDL):
+
+Name       | Type                       | Min  | Max 
+-----------|----------------------------|------|---
+UInt8      | unsigned 8-bit integer     |0     | 255
+Int8       | signed 8-bit integer       | -128 | 127
+UInt16     | unsigned 16-bit integer    |  0   | 65535 
+Int16      | signed 16-bit integer      | -32768 | 32767
+UInt32     | unsigned 32-bit integer    | 0 | 4294967295
+Int32      | signed 32-bit integer      | -2147483648 | 2147483647
+UInt64     | unsigned 64-bit integer    | 0    | 2^64
+Int64      | signed 64-bit integer      | -2^63 | 2^63 - 1
+Boolean    | boolean value              | 0/false | 1/true
+Float      | floating point number      | -3.4e -38 | 3.4e 38
+Double     | double precision floating point number | -1.7e -300 | 1.7e 300
+String     | character string           | n/a  | n/a
+ByteBuffer | buffer of bytes (aka BLOB) | n/a | n/a
+
+## SIGNAL RANGE [OPTIONAL]
+A signal can optionally be specified with a min and max limit,
+defining a range that the signal can assume a value within.
+
+## SIGNAL ENUMERATION [OPTIONAL]
+A signal can optionally be specified with a set of allowed values that
+the signal can take, effectively turning it into an enumerator.  The
+values are of the same type as the signal itself.
+
+## SIGNAL UNIT TYPE [OPTIONAL]
+A signal can optionally specify a unit type from the following set:
+
+Unit type  | Domain | Description       
+-----------|---------------------
+kph        | Speed       | Kilometers per hour
+celsius    | Temperature | Degrees celsius
+mbar       | Pressure    | millibar
+percent    | Percent     | Percent
+hz         | frequency   | Frequency
+lat        | position    | Decimal latitude 
+lon        | position    | Decimal longitude
+millimeter | distance    | Millimeter
+meter      | distance    | Meter
+kilometer  | distance    | Kilometer
+[more to come] ||
+
+## SIGNAL NAMING CONVENTION
+Signals are named, left-to-right, from the root of the signal tree
+toward the signal itself. Each element in the name is deliniated with
+a period (".") .
+
+In Fig 1 above the left mirror heated signal would be:
+
+    body.mirrors.left.heated
 
 
-Signal naming convention
-
-Node vs. tree
-What constitutes a signal
-Setter vs. Current signals
-Interval
-
 
 
 # SIGNAL SPECIFICATION FORMAT
 
 ## ENTRY
 
+### TYPE
+### INTERVAL
+### ENUMERATION
+
 ## FILE
 
 ## INCLUDE DIRECTIVES
diff --git a/pics/tree.png b/pics/tree.png
index 3eb0cd22e..179aa5309 100644
Binary files a/pics/tree.png and b/pics/tree.png differ
diff --git a/root.vspec b/root.vspec
index b0af65d5f..2a4886227 100644
--- a/root.vspec
+++ b/root.vspec
@@ -68,6 +68,16 @@ something.vsi
 	"description": "0=max forward. 100=max backward"
 }
 
+{
+	"name": "seats.0.massage_level"
+  	"type": {
+		"type": "Uint16",
+		"unit_type": "percent",
+		"enum": [ 1,2,5,6,12]
+	}
+	"description": "0=max forward. 100=max backward"
+}
+
 {
 	"name": "seats.driver_seat.position"
   	"type": {