Erlewine, Michael Yoshitaka and Hadas Kotek, 2016. “The structure and interpretation of non-restrictive relatives: Evidence from relative pronoun pied-piping.”
Proceedings of the 51st Meeting of the Chicago Linguistic Society (CLS 51), pages 149–163.

English is one of many languages in which relative clauses (RC) can be constructed using wh-words as relative pronouns. The relative pronoun originates lower in the clause and A-moves to the edge of the RC. This movement can pied-pipe other material with it, resulting in relative pronoun pied-piping (RPPP).

In this paper, we investigate the structure and interpretation of English non-restrictive relative clauses. We propose that in non-restrictive relatives, relative pronouns are interpreted in-situ within the pied-piped constituent at LF, using Rooth- Hamblin alternative computation (Hamblin, 1973; Rooth, 1985, 1992, a.o.). Evidence comes from the presence of intervention effects in RPPP; intervention effects (Beck, 2006; Sauerland & Heck, 2003, a.o.) can be used to diagnose regions of alternative computation (see Kotek & Erlewine, to appear; Erlewine & Kotek, 2014). The proposal here has the consequence that non-restrictive relatives are fundamentally proposition-denoting in contrast to restrictive relatives which are property-denoting.

See also Intervention effects in relative pronoun pied-piping: experimental evidence in SuB 20 for supporting experimental evidence.