Both types of gerunds exhibit a similar distribution, appearing in most places where NP's are allowed.18.1 The bold face portions of sentences ((301))-((303)) show examples of gerunds as a subject and as the object of a preposition.
The motivation for splitting the gerunds into two classes is semantic as well as structural in nature. Semantically, the two gerunds are in sharp contrast with each other. NP gerunds refer to an action, i.e., a way of doing something, whereas determiner gerunds refer to a fact. Structurally, there are a number of properties (extensively discussed in [#!Lees60!#]) that show that NP gerunds have the syntax of verbs, whereas determiner gerunds have the syntax of basic nouns. Firstly, the fact that the direct object of the determiner gerund can only appear within an of PP suggests that the determiner gerund, like nouns, is not a case assigner and needs insertion of the preposition of for assignment of case to the direct object. NP gerunds, like verbs, need no such insertion and can assign case to their direct object. Secondly, like nouns, only determiner gerunds can appear with articles (cf. example ((304)) and ((305))). Thirdly, determiner gerunds, like nouns, can be modified by adjectives (cf. example ((306))), whereas NP gerunds, like verbs, resist such modification (cf. example ((307))). Fourthly, nouns, unlike verbs, cannot co-occur with aspect (cf. example ((308)) and ((309))). Finally, only NP gerunds, like verbs, can take adverbial modification (cf. example ((310)) and ((311))).
In English XTAG, the two types of gerunds are assigned separate
trees within each tree family, but in order to capture their similar
distributional behavior, both are assigned NP as the category label of
their top node. The feature gerund = +/- distinguishes gerund NP's from
regular NP's where needed.18.2 The determiner gerund
and the NP gerund trees are discussed in section (18.1) and
(18.2) respectively.