FIXUP: Got the order of probability tables wrong

format.md

@@ -61,7 +61,10 @@ ProbabilityTable ::= ProbabilityTableUnreachable     # Compression artifact. A t
                  |   ProbabilityTableIndexedSymbols  # Used for enums, booleans, sums of interfaces.
 ```
 
-The order of probability tables is meaningful.
+The probability tables are written down in an order extracted from the grammar and define a model
+`table: (parent type, my type) -> [(value, probabilities)]`.
+
+FIXME: Specify how the order is extracted from the grammar.
 
 ```
 ProbabilityTableUnreachable ::= 0x02
@@ -127,12 +130,4 @@ ListPength(parent) ::= Value((parent, 'list-length')) # List lengths are u32 val
 Primitive(parent) ::= bit*
 ```
 
-To determine how many bits need to be read to decode a `Primitive(parent)`, it is sufficient for a decoder to know the distribution of probabilities for `(parent, expected type)`.
-
-For this purpose, the decoder maintains a mapping `models: (parent, expected type) |-> distribution`.
-
-Initially, this mapping is empty. Whenever we encounter a `Primitive(parent)` for an expected type:
-
-- if `models(parent expected type)` is empty, read the next table in `ProbabilityPrelude`, and this becomes the value
-    result of `models(parent expected type)`;
-- otherwise, use `models(parent expected type)`.
+To determine how many bits need to be read to decode a `Primitive(parent)`, it is sufficient for a decoder to know the distribution of probabilities for `(parent, expected type)`, as stored in the `ProbabilityPrelude`.