Dependency-based Parse Trees
The dependency-based parse trees of dependency grammars see all nodes as terminal, which means they do not acknowledge the distinction between terminal and non-terminal categories. They are simpler on average than constituency-based parse trees because they contain many fewer nodes. The dependency-based parse tree for the example sentence above is as follows:
This parse tree lacks the phrasal categories (S, VP, and NP) seen in the constituency-based counterpart above. Like the constituency-based tree however, constituent structure is acknowledged. Any complete subtree of the tree is a constituent. Thus this dependency-based parse tree acknowledges the subject noun John and the object noun phrase the ball as constituents just like the constituency-based parse tree does.
The constituency vs. dependency distinction is far-reaching. Whether the additional syntactic structure associated with constituency-based parse trees is necessary or beneficial is a matter of debate.
Read more about this topic: Parse Tree
Famous quotes containing the word trees:
“Usually the scenery about them is drear and savage enough; and the logger’s camp is as completely in the woods as a fungus at the foot of a pine in a swamp; no outlook but to the sky overhead; no more clearing than is made by cutting down the trees of which it is built, and those which are necessary for fuel.”
—Henry David Thoreau (1817–1862)