Updated Persister (.world etc.) format (markdown)

Persister-(.world-etc.)-format.md

@@ -1,6 +1,6 @@
 Data in Persister format does not mark itself to indicate their types, the types are assumed by the deserialization code. That is, a Portal being read in knows when to expect a boolean, a string, and an integer, for example. Without knowing what a Portal wants to read, it is not possible to determine where the next item begins.
 
-During reading or writing, WorldsPlayer maintains 3 tables: Object table, Class table, Cookie table (for versions). These serve as a caching mechanism, 
+During reading or writing, WorldsPlayer maintains 3 tables: Object table, Class table, Cookie table (for versions). These serve as a caching mechanism, so that objects can be reused and class names do not need to be repeated.
 
 # Primitive data types
 
@@ -9,6 +9,10 @@ Worlds generally uses the format described by [Java's DataInput](https://docs.or
 * String: Starts with a byte, where 0x01 means the string is null (and the next byte is for the next item) and 0x00 means non-null. If non-null, next 2 bytes are the length in number of bytes (big-endian). Following is the actual string data, in modified UTF-8. (The bytes after the non-null indicator are merely read by DataInput).
 * Boolean: 1 byte, 0x00 for false 0x01 for true.
 * Byte, Double, Long, Int, Float, Short: Self-explanatory
+* Arrays, vectors, maybenulls: Explained below 
 
 # Objects
-Obj
+
+Assuming empty class and object table, an object consists of an object ID (integer), a class ID (integer), class name (String), and then data as determined by the specific class.
+
+## Example from GroundZero