Path Containment Condition

Path Containment Condition is a condition which attempts to give a generalized account of constraints on crossing and nested dependencies, such as the Subject condition and the ECP. The condition states that if two paths overlap, one must contain the other. The following contrast illustrates the general idea:

(i) * Whoi did you wonder [CP whatj ti saw tj] (ii)  Whatj did you wonder [CP whoi ti saw tj]

Assume that there is a path connecting each wh-phrase to its trace. In both (i) and (ii), the two paths overlap, so the PCC applies. In (i), the path of who 'crosses' the path of what, in violation of the PCC and the sentence is ungrammatical. In (ii) on the other hand, the path of who is 'contained' in the path of what. Hence (ii) obeys the PCC and the sentence is grammatical. See Connectedness.

Links
Utrecht Lexicon of Linguistics