PARR

PARR is a requirement that an elliptic second conjunct is interpreted in the same way as the first conjunct.

Example
given that (i)a can be understood either as (i)b or as (i)c, one would expect (ii)a to have the interpretations (ii)b-e. PARR however does not allow the interpretations (ii)c and e, in which the second conjunct is not interpreted parallel to the first conjunct.

(i)  a	 Bill wants to buy a book b	 there is a book that Bill wants to buy c	 Bill wants there to be a book for him to buy (ii) a	 Bill wants to buy a book and John does too b	 there is a book that Bill wants to buy and there is a book that John wants to buy c	 there is a book that Bill wants to buy and John wants there to be a book for him to buy d	 Bill wants there to be a book for him to buy and John wants there to be a book for him to buy e	 Bill wants there to be a book for him to buy and there is a book that John wants to buy

Links
Utrecht Lexicon of Linguistics