edu.stanford.nlp.trees.tregex
Class TreePattern

java.lang.Object
  edu.stanford.nlp.trees.tregex.TreePattern

public class TreePattern
extends Object

A TreePattern is a tgrep-type pattern. Instances of it can be matched against instances of the Tree class.

Currently supported node/node relations and their symbols:

Symbol	Meaning
A << B	A dominates B
A >> B	A is dominated by B
A < B	A immediately dominates B
A > B	A is immediately dominated by B
A $ B	A is a sister of B (and not equal to B)
A .. B	A precedes B
A . B	A immediately precedes B
A <<, B	B is a leftmost descendent of A
A <<- B	B is a rightmost descendent of A
A >>, B	A is a leftmost descendent of B
A >>- B	A is a rightmost descendent of B
A <, B	B is the first child of A
A >, B	A is the first child of B
A <- B	B is the last child of A
A >- B	A is the last child of B
A <i B	B is the ith child of A (i > 0)
A >i B	A is the ith child of B (i > 0)
A <-i B	B is the ith-to-last child of A (i > 0)
A >-i B	A is the ith-to-last child of B (i > 0)
A <: B	B is the only child of A
A $++ B	A is a left sister of B
A $-- B	A is a right sister of B
A $+ B	A is the immediate left sister of B
A $- B	A is the immediate right sister of B
A <+C B	A dominates B via an unbroken chain of (zero or more) nodes matching description C
A >+C B	A is dominated by B via an unbroken chain of (zero or more) nodes matching description C
A <<# B	B is a head of phrase A
A >># B	A is a head of phrase B
A <# B	B is the immediate head of phrase A
A ># B	B is the immediate head of phrase A

Note that the operators are implicitly left-associative, so that "S < VP < NP" is equivalent to "(S < VP) < NP", which matches something where both a VP and an NP are directly below the S (in no particular order), like

     (S (NP (NNP Juan))
        (VP (VBD tried)))
 

If instead what you want is an NP below a VP below an S, you should write "S < (VP < NP)".

Current known bugs/shortcomings:

• Node search currently takes no advantage of limitations imposed by the queried relations. This reduces the efficiency of the search, quite a bit in some cases.

Author:

Roger Levy

Method Summary

static TreePattern	compile(String str) Compiles the given tree expression into a TreePattern instance.
boolean	findNext()
static void	main(String[] args) Used to check how tree patterns are compiled, and how node descriptions are compiled into regular expressions.
TreeMatcher	matcher(Tree t) Creates a TreeMatcher that can match this pattern to the specified input tree.
String	pattern() returns the tree-pattern expression from which the pattern was compiled.
void	reset(Tree root)
Tree	returnMatch()
void	setCurrentResult(edu.stanford.nlp.trees.tregex.TreePatternReturnValue currentResult)
String	toString() Returns a representation of the TreePattern

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

matcher

public TreeMatcher matcher(Tree t)

Creates a TreeMatcher that can match this pattern to the specified input tree.

compile

public static TreePattern compile(String str)

Compiles the given tree expression into a TreePattern instance.

toString

public String toString()

Returns a representation of the TreePattern

Overrides:

toString in class Object

pattern

public String pattern()

returns the tree-pattern expression from which the pattern was compiled.

reset

public void reset(Tree root)

findNext

public boolean findNext()

returnMatch

public Tree returnMatch()

setCurrentResult

public void setCurrentResult(edu.stanford.nlp.trees.tregex.TreePatternReturnValue currentResult)

main

public static void main(String[] args)

Used to check how tree patterns are compiled, and how node descriptions are compiled into regular expressions.