POS ambiguity. In the case of ambiguous POS tags, it is sometimes possible to constrain the ambiguity to a choice between two (or even three) options. When that is possible, that is what we do (rather than simply using the blanket tag X). The possibilities are concatenated using underline, as in the following examples. In general, the options are listed in alphabetical order.
( (CP-QUE-MAT (WADVP (WADV How@)) (IP-SUB (DOD_MD @'d) (NP-SBJ (PRO you)) (VP (DO do) (NP-OB1 (D that)))) (PUNC ?))) ( (CP-QUE-MAT (WADVP (WADV How@)) (IP-SUB (HVD_MD @'d) (NP-SBJ (PRO they)) (VP (VB_VBN set) (NP-OB1 (D that)) (RP up))) (PUNC ?)))
Syntactic ambiguity. For syntactic ambiguity, indicating the various options is not feasible, and so we establish default annotations for difficult cases. These are documented as needed in connection with the relevant topics.