Why does this fail <slots.keys:{ key | <reading(key, slots.(key))> }; separator="\n"> >> reading(number,slots) ::= << >> while this works fine? <slots.keys:{ key | <reading(slots.(key))> }; separator="\n"> >> reading(slots) ::= << >> The underlying object is of type Map<Integer, Collection<Slot>> Any idea? cheers -- Torsten