joshua.decoder.chart_parser.DotChart Class Reference

Collaboration diagram for joshua.decoder.chart_parser.DotChart:

List of all members.

Classes
class	DotCell
class	DotNode
Public Member Functions
DotCell	getDotCell (int i, int j)
	DotChart (Lattice< Token > input, Grammar grammar, Chart chart, NonterminalMatcher nonTerminalMatcher, boolean regExpMatching)
Package Functions
void	seed ()
void	expandDotCell (int i, int j)
void	startDotItems (int i, int j)
Private Member Functions
void	extendDotItemsWithProvedItems (int i, int k, int j, boolean skipUnary)
ArrayList< Trie >	matchAll (DotNode dotNode, int wordID)
void	addDotItem (Trie tnode, int i, int j, ArrayList< SuperNode > antSuperNodesIn, SuperNode curSuperNode, SourcePath srcPath)
Private Attributes
ChartSpan< DotCell >	dotcells
Chart	dotChart
Grammar	pGrammar
final int	sentLen
final Lattice< Token >	input
final boolean	regexpMatching
final NonterminalMatcher	nonTerminalMatcher
Static Private Attributes
static final Logger	logger = Logger.getLogger(DotChart.class.getName())

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Detailed Description

The DotChart handles Earley-style implicit binarization of translation rules.

The DotNode object represents the (possibly partial) application of a synchronous rule. The implicit binarization is maintained with a pointer to the Trie node in the grammar, for easy retrieval of the next symbol to be matched. At every span (i,j) of the input sentence, every incomplete DotNode is examined to see whether it (a) needs a terminal and matches against the final terminal of the span or (b) needs a nonterminal and matches against a completed nonterminal in the main chart at some split point (k,j).

Once a rule is completed, it is entered into the DotChart. DotCell objects are used to group completed DotNodes over a span.

There is a separate DotChart for every grammar.

Author:

Zhifei Li, zhife.nosp@m.i.wo.nosp@m.rk@gm.nosp@m.ail..nosp@m.com

Matt Post post@.nosp@m.cs.j.nosp@m.hu.ed.nosp@m.u

Kristy Hollingshead Seitz

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Constructor & Destructor Documentation

joshua.decoder.chart_parser.DotChart.DotChart	(	Lattice< Token >	input,
		Grammar	grammar,
		Chart	chart,
		NonterminalMatcher	nonTerminalMatcher,
		boolean	regExpMatching
	)

Constructs a new dot chart from a specified input lattice, a translation grammar, and a parse chart.

Parameters:

input	A lattice which represents an input sentence.
grammar	A translation grammar.
chart	A CKY+ style chart in which completed span entries are stored.

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Member Function Documentation

void joshua.decoder.chart_parser.DotChart.addDotItem	(	Trie	tnode,
		int	i,
		int	j,
		ArrayList< SuperNode >	antSuperNodesIn,
		SuperNode	curSuperNode,
		SourcePath	srcPath
	)		[private]

Creates a DotNode and adds it into the DotChart at the correct place. These are (possibly incomplete) rule applications.

Parameters:

tnode	the trie node pointing to the location ("dot") in the grammar trie
i
j
antSuperNodesIn	the supernodes representing the rule's tail nodes
curSuperNode	the lefthand side of the rule being created
srcPath	the path taken through the input lattice

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void joshua.decoder.chart_parser.DotChart.expandDotCell	(	int	i,
		int	j
	)		[package]

This function computes all possible expansions of all rules over the provided span (i,j). By expansions, we mean the moving of the dot forward (from left to right) over a nonterminal or terminal symbol on the rule's source side.

There are two kinds of expansions:

1. Expansion over a nonterminal symbol. For this kind of expansion, a rule has a dot immediately prior to a source-side nonterminal. The main Chart is consulted to see whether there exists a completed nonterminal with the same label. If so, the dot is advanced.

   Discovering nonterminal expansions is a matter of enumerating all split points k such that i < k and k < j. The nonterminal symbol must exist in the main Chart over (k,j).

2. Expansion over a terminal symbol. In this case, expansion is a simple matter of determing whether the input symbol at position j (the end of the span) matches the next symbol in the rule. This is equivalent to choosing a split point k = j - 1 and looking for terminal symbols over (k,j). Note that phrases in the input rule are handled one-by-one as we consider longer spans.

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void joshua.decoder.chart_parser.DotChart.extendDotItemsWithProvedItems	(	int	i,
		int	k,
		int	j,
		boolean	skipUnary
	)		[private]

Attempt to combine an item in the dot chart with an item in the main chart to create a new item in the dot chart. The DotChart item is a DotNode begun at position i with the dot currently at position k, that is, a partially-applied rule.

In other words, this method looks for (proved) theorems or axioms in the completed chart that may apply and extend the dot position.

Parameters:

i	Start index of a dot chart item
k	End index of a dot chart item; start index of a completed chart item
j	End index of a completed chart item
skipUnary	if true, don't extend unary rules

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DotCell joshua.decoder.chart_parser.DotChart.getDotCell	(	int	i,
		int	j
	)

ArrayList<Trie> joshua.decoder.chart_parser.DotChart.matchAll	(	DotNode	dotNode,
		int	wordID
	)		[private]

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void joshua.decoder.chart_parser.DotChart.seed

(

)

[package]

Add initial dot items: dot-items pointer to the root of the grammar trie.

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void joshua.decoder.chart_parser.DotChart.startDotItems	(	int	i,
		int	j
	)		[package]

note: (i,j) is a non-terminal, this cannot be a cn-side terminal, which have been handled in case2 of dotchart.expand_cell add dotitems that start with the complete super-items in cell(i,j)

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Member Data Documentation

ChartSpan<DotCell> joshua.decoder.chart_parser.DotChart.dotcells [private]

Two-dimensional chart of cells. Some cells might be null. This could definitely be represented more efficiently, since only the upper half of this triangle is every used.

Chart joshua.decoder.chart_parser.DotChart.dotChart [private]

CKY+ style parse chart in which completed span entries are stored.

final Lattice<Token> joshua.decoder.chart_parser.DotChart.input [private]

final Logger joshua.decoder.chart_parser.DotChart.logger = Logger.getLogger(DotChart.class.getName()) [static, private]

final NonterminalMatcher joshua.decoder.chart_parser.DotChart.nonTerminalMatcher [private]

Grammar joshua.decoder.chart_parser.DotChart.pGrammar [private]

Translation grammar which contains the translation rules.

final boolean joshua.decoder.chart_parser.DotChart.regexpMatching [private]

final int joshua.decoder.chart_parser.DotChart.sentLen [private]