<P> There are two established and competing principles for constructing trees; they produce' constituency' and' dependency' trees and both are illustrated here using an example sentence . The constituency - based tree is on the left and the dependency - based tree is on the right: </P> <Dl> <Dd> <Dl> <Dd> </Dd> </Dl> </Dd> </Dl> <Dd> <Dl> <Dd> </Dd> </Dl> </Dd> <P> The tree on the left is of the constituency - based, phrase structure grammar, and the tree on the right is of the dependency grammar . The node labels in the two trees mark the syntactic category of the different constituents, or word elements, of the sentence . </P>

Which of these is the most accurate summary based on key words in this paragraph