SFI connects "filler" subjects "it" and "there" to invertible verbs in questions with subject-verb inversion:
+SFI+
| |
Is it likely that Jane will go
Is there going to be a problem
Both the use of "it" and "there" and the use of subject-verb
inversion are highly constrained by post-processing (see
"SF";
see "SI").
However, there is nothing especially problematic
about SFI; SFI is to SF precisely as
SI is to S.