For right-branching structures , the leftcorner ancestor is the parent , conditioning on which has been found to be beneficial ( Johnson , 1998 ) , as has conditioning on the left-corner child ( Roark and Johnson , 1999 ) .
efficient probabilistic topdown and leftcorner parsing
Brian Roark Mark Johnson
These nodes are the left-corner ancestor of top , ( which is below top , on the stack ) , top 's left-corner child ( its leftmost child , if any ) , and top 's most recent child ( which was top , _ 1 , if any ) . For right-branching structures , the leftcorner ancestor is the parent , conditioning on which has been found to be beneficial ( Johnson , 1998 ) , as has conditioning on the left-corner child ( Roark and Johnson , 1999 ) . Because these inputs include the history features of both the leftcorner ancestor and the most recent child , a derivation step i always has access to the history features from the previous derivation step i -- 1 , and thus ( by induction ) any information from the entire previous derivation history could in principle be stored in the history features .
For right-branching structures , the leftcorner ancestor is the parent , conditioning on which has been found to be beneficial ( Johnson , 1998 ) , as has conditioning on the left-corner child ( @@CITATION ) .