Here is the definition of a data type in nwndynlib-2.0.
A data type is a variable type for which the following
conditions are met:
-# any data of this type can be replicated to form an
identical copy;
-# all information necessary for replicating the data
can be extracted from the variable;
-# all information necessary for replicating the data
can be stored as local variables through the script engine;
-# the type has a default, 'INVALID', value;
-# there is a mechanism to establish if a value is
valid or invalid;
-# there is a mechanism to establish equality between
two copies of the data;
-# if value1 is invalid, and value2 is invalid, then
value1 is equal to value2, even if they are not copies
of the same data.