A further problem concerning the syntax of adjuncts is posed by the fact that adjuncts can take part in unbounded dependency constructions. Lexical treatments of the kind presented in [7, chapter 9] assume that a lexical rule is responsible for `moving' an element from the subcat list to the slash list. Such an account predicts that adjuncts can not take part in such unbounded dependency constructions. In [7, chapter 9] a special rule is introduced to account for those cases where adjuncts do take part in UDCs. The treatment that we propose for adjuncts obviates the need for such an `ad-hoc' rule.
Clearly many details concerning the syntax of adjuncts are left untouched here, such as the quite subtle restrictions in word-order possibilities of certain adjuncts with respect to arguments and with respect to other adjuncts. In the current framework linguistic insights concerning these issues could be expressed as constraints on the resulting subcategorization list (e.g. by means of LP-constraints).
It should also be stressed that treating adjuncts and arguments on a par on the level of subcategorization does not imply that observed differences in the behavior of adjuncts and arguments could not be handled in the proposed framework. For example the difference of adjuncts and arguments in the case of left dislocation in Dutch (exemplified in 13-16) can be treated by a lexical rule that operates on the subcat list before adjuncts are added.