Top Down
An important aspect of phrase structure rules is that they view sentence structure from the top down. The category on the left of the arrow is a greater constituent and the immediate constituents to the right of the arrow are lesser constituents. Constituents are successively broken down into their parts as one moves down a list of phrase structure rules for a given sentence. This top-down view of sentence structure stands in contrast to much work done in modern theoretical syntax. In Minimalism for instance, sentence structure is generated from the bottom up. The operation Merge merges smaller constituents to create greater constituents until the greatest constituent (i.e. the sentence) is reached. In this regard, theoretical syntax abandoned phrase structure rules long ago, although their importance for computational linguistics seems to remain intact.
Read more about this topic: Phrase Structure Rules
Famous quotes containing the words top down and/or top:
“Kindliness seems to exist primarily as an animal instinct, so deeply rooted that mental degeneracy, which works from the top down, does not destroy it until the mind sinks to the lower grades of idiocy.”
—Charles Horton Cooley (1864–1929)
“The Star that bids the Shepherd fold,
Now the top of Heav’n doth hold,
And the gilded Car of Day,
His glowing Axle doth allay
In the steep Atlantick stream,”
—John Milton (1608–1674)
“I can’t forget
How she stood at the top of that long marble stair
Amazed, and then with a sleepy pirouette
Went dancing slowly down to the fountain-quieted square;”
—Richard Wilbur (b. 1921)