Will and I have briefly discussed l3messages, and I thought I'd summarise for the list a few observations: - The module prefix \err is not really that helpful, as some of the functions are related to information rather than errors: would \msg_ be better (at least for the non-error parts)? - Saving the error messages to file to save memory is not really relevant today, especially as every message needs a tlp in any case. - On the other hand, perhaps having the errors in this way makes localisation of messages easier? Is this something that should be considered, and if so an alternative mechanism is needed. - The interface is not that helpful. As well as some problems creating messages, there is no easy way to re-create \PackageInfo, etc. from LaTeX2e: no automated adding of package name, etc. This leaves the programmer to sort out their own system (or not). - The messages themselves need some attention. Compared to LaTeX2e messages, some extra lines of code appear in the output that don't really help. Currently, \g_file_curr_name_tlp is set to "no file" and (apparently) never changed elsewhere. So messages never give a clue to the file concerned. - Some parts of the file are not documented (for example \text_put_sp:). Over all, I'd suggest this needs some attention, but first some kind of updated structure should be agreed. -- Joseph Wright