PolyGen is a program for generating random
sentences according to a grammar definition, that
is following custom syntactical and lexical rules.
Formally, it is an interpreter of a language
itself designed to define languages, where to
interpret means executing a source program in real
time and eventually outputting its result. Here, a
source program is a grammar definition. The
execution consists of the exploration of such
grammar by selecting a random path, and the result
is the sentence built on the way.
