The formal model of Compositional Network Architecture is referred to in the book, but can only be found on this site. Its documentation explains what is in the model, how it works, and what it means.

The formal model is written in the modeling language Alloy (see the Alloy site for documentation and downloads). The formal model (.zip file) consists of five files, each of which comes in two versions: file.als runs in the Alloy Analyzer, while file.num has line numbers referenced in the documentation.