When I learnt grammar in school, I was taught that there are optional and obligatory adverbials. Trying to understand grammar in the form presented by Huddleston and Pullum (e.g. the Cambridge Grammar of the English Language and A Student’s Introduction to English Grammar), I’m wondering how to deal with “obligatory adverbials” such as the following:
(1) He is in the garden.
(2) He was on his way.
(3) He went there.
(4) His birthday is today.
If I’m not completely mistaken, the PPs in (1) and (2) would simply be called PP complements, but what about the phrases in (3) and (4)? Are they too PP complements, in line with the rather drastic re-analysis the authors suggest for adverbs/prepositions/subordinators?
You are correct about (1) and (2)—CGEL would say they are locative complements in the form of a PP.
You are also correct about (3). CGEL does explicitly say that there is a preposition on p. 640, in the context of discussing prepositions whose complement is another PP:
The PPs here, there, now, then occur as complement to a wider range of prepositions than do such PPs as under the bed or after six. We find, for example, They live near here; Put it on there; I found it behind here; You should have told me before now; He certainly stayed past then.
However, CGEL says (p. 429) that today is not a preposition, but a deictic temporal pronoun:
Yesterday, today, tonight, and tomorrow are not traditionally analysed as pronouns, but belong in this subclass of nouns by virtue of their inability to take determiners. Compare, for example, Today/*The today is my birthday. They are also semantically like the central pronouns I and you in that they are characteristically used deictically. Unlike the temporal prepositions now and then, the pronouns have genitive forms: today’s, etc.
As far as whether locative in locative complement is a syntactic or semantic characterization, CGEL seems to claim the former. On p. 257, in the section ‘Relation between locative complements and predicative complements’:
We will not assimilate the locatives to the predicatives, but will regard them as syntactically distinct kinds of complement that exhibit certain semantic resemblances.