Anthony Travers wished for:

"A technical document defining the format of Hat traces, so that implementors of Haskell can add native support for Hat to their respective systems."

Great idea! Do the documents at http://www.cs.york.ac.uk/fp/hat/Memos/ come close? Especially these ones: 14 Hat File Format 19 A Better Hat File Format 31 The Definition of the Augmented Redex Trail Regards, Malcolm