Pollard and Sag (1987) also point out that in English adjuncts tend to be ordered after complements, suggesting that prepositional phrases which are required to precede other kinds of adjuncts (i.e. which cannot be flexibly interspersed with other adjuncts) are actually complements.
The data in d24-d31 suggest that the dative prepositional phrases should be treated as complements according to the relative order diagnostic. These PPs must appear before any other adjunctive phrases.
Adam gave a book to Debbie in the library.
*Adam gave a book in the library to
Debbie.
Adam told a story to the children in the bedroom. *Adam told a story in the bedroom to the children.
Adam sent a letter to Mary at the post office. *Adam sent a letter at the post office to Mary.
Adam kicked a ball to Mary in the park. *Adam kicked a ball in the park to Mary.
Adam baked a cake for Mary in the kitchen. ? Adam baked a cake in the kitchen for Mary.
Adam sang a song for Mary in the pub. ? Adam sang a song in the pub for Mary.