Focus alternatives may be computed as semantic objects (Rooth 1985, 1992) or as syntactic objects (e.g. Fox & Katzir 2011). We provide evidence that syntax plays a role based on polar questions in Turkish. There is morphological evidence that the Hamblin set for the polar question is formed via focus alternatives (e.g. Atlamaz 2023). Computing alternatives as semantic objects would over-generate answers in the Hamblin set. On the other hand, the target Hamblin set can be naturally predicted in the syntactic approach, provided that alternatives involve replacing the focus with constituents of the same syntactic category.
Türk et al. (Fri,) studied this question.