Constituent Structure - Part 24 | 40 PRELIMINARIES relations immediate dominance in combination with the orderings of elements among sisters. We will assume that sisters are always ordered left to right on a single line so problems like those in trees like 21 will not arise. This ordering is a 24 We might call the relation in question here 24 Sister Precedence s Node A sister-precedes node B if and only if both are immediately dominated by the same node M and A emerges from a branch from M that is to the left of the branch over B. General precedence then can be defined parasitically on sister precedence 25 Precedence Node A precedes node B if and only if i neither A dominates B nor B dominates A and ii some node E dominating A sister-precedes some node F dominating B because domination is reflexive E may equal A and F may equal B but they need not do so . Recall our badly drawn tree in 22 . There is a node NP E in the definition above which dominates the N clown and that NP sister-precedes the VP F which in turn dominates V kissed NP . Therefore N clown precedes V kissed. This definition in particular part ii also derives a typical restriction on syntactic branches may not cross. So trees like that in 26 are disallowed. In this tree Q is written to the left of R apparently preceding R but by the definition of precedence given above this tree is ruled out. Q is to the left of R but O which dominates Q is sister-preceded by N. In other words branches may not cross. We will revisit this issue in Chapter 10. 23 But might be due to the ordering in the phrase structure rule or other generative principle of linearization. 24 Sister-precedence is a relation that captures the exhaustive constant partial ordering ECPO insight of GPSG Gazdar Klein Pullum and Sag 1983 where precedence relations hold only in local trees and between local trees. BASIC PROPERTIES OF TREES 41 Immediate precedence There is also the local form of precedence immediate precedence 25 27 Immediate
