This work is concerned with a previously undescribed phenomenon of what I call structured questions, which are questions that raise two hierarchically related QUDs (Questions Under Discussion). Below are examples from Turkish.
An ordinary alternative question:
1. Şarap mı istiyor-sun, bira mı, yoksa rakı mı?
wine Q want-2sg, beer Q, yoksa rakı Q
Do you want wine, beer or rakı?
(exhaustive, equally prominent alternatives)
A structured alternative question:
2. Şarap mı istiyor-sun, yoksa bira mı, rakı mı?
wine Q want-2sg, yoksa beer Q, rakı Q
Do you want wine, if not would you like beer or rakı?
(exhaustive or not, wine is a more prominent option than the others)
The difference in form between these alternative questions is the position of the particle yoksa. I provide a semantics for the particle yoksa, analyzing it as introducing the last uttered possible answer to a QUD.
The semantics of yoksa, and the effect it has on the syntactic structure of the question, are enough to explain the special semantics of structured questions, i.e. the availability of non-exhaustivity, and the internal hierarchical QUD structure, which manifests itself through the difference in prominence of the alternatives.