Most editing rules are syntactic rules rather than information deletions or
lexical substitutions. I have already outlined how rules are applied to repair
ungrammatical structures after constituents have been deleted. Such
structure-mending rules are obligatory and often accomplish major reorganizations
of surface constituents. They are required particularly but not
exclusively after deletion rules. Depronominalization commonly becomes
obligatory after deletion of its antecedent; without such deletion, depronominalization
would be an optional reversal.