My biggest problem (at the moment) is that the trace file format is under-documented. I've written my new back-end by reverse-engineering existing back-ends, but that's too error-prone for comfort. Is there any unpublished documentation on the trace file format and its correct interpretation that might help me ensure I'm not missing anything crucial?
Indeed, there is a lot of unpublished documentation about Hat. We had a series of internal memos covering lots of design issues including the file format. Up until now, these have been private, but I can't think of a good reason for them to remain that way, especially if other people are developing on top of Hat and need to understand such issues. So have a look at http://www.cs.york.ac.uk/fp/hat/Memos Bearing in mind that many of the memos may now be superseded or out of date, I hope that nevertheless you manage to find something useful here. (There are two separate memos about the file format, one by me, another by Olaf.) Regards, Malcolm