Difficulty with this approach arises when f-structure heads are assigned discourse functions. When these heads are assigned a discourse function role, everything within the sub-f-structure containing the head is also contained within the discourse function. Although this sometimes gives the correct scope of the discourse function, it usually results in wider scope than desired. That is, more material is topicalised or focused than was intended.
This problem is illustrated below by three different types of focus assignment in Russian. Neutral yes-no questions received the correct, wide-scope focus interpretation, although they give rise to a circular f-structure. However, contrastive focus of verbs and new-information focus of the VP cannot be assigned correctly by this approach.