Return the tree if it has been simplified

[Ezibenroc]

On query ((1984, author, ?), foo, ?) this module should return (George Orwell, foo, ?).

[Tpt]

This simple problem uncovers a lot of things so I don't know when I'll find a nice way to solve this issue. If you want we can talk about it (it would take more than 1/2h to write down all possible solutions and their pro/cons).