Hello all, A few points to be clarified came up via the TeX StackExchange chat system [http://chat.stackexchange.com/transcript/message/4850082#4850082] Taking the example of the l3prop module \prop_put:nn is a function of the prop module that can be used by other modules. In other words it is a public interface. On the other hand \prop_put_aux:NNnn, called by \prop_put:nn and others, is an internal function, and so would be renamed as \__prop_put_aux:NNnn or possibly \__prop_put:NNnn (as the _aux is not directly needed here). As such, 'well behaved' LaTeX3 module will still have access to exactly the same functions from the kernel as they do now, and via the same names. It is only functions which are 'private' to a single module which would be changed. -- Joseph Wright