That is the generator is not free to produce any NL variant verbalising the query but should produce a verbalisation that is linearly as close as possible, modulo the revision applied by the user, to the query before revisions.
for instance, given the DL query (2) and assuming a linearisation of that formula that matches the linear order it is presented in (see Section 4.2.1 below for a definition of the linearisation of DL formulae), sentence (2b) will be preferred over (2c).