edu.stanford.nlp.ie.hmm
Class Structure

java.lang.Object
  |
  +--edu.stanford.nlp.ie.hmm.Structure

All Implemented Interfaces:

GeneralStructure, Serializable

Direct Known Subclasses:

MultiStructure

public class Structure

extends Object

implements GeneralStructure, Serializable

Class to model an HMM structure. This builds a straightforward one-target-state structure, via a series of structure building operations. It can be used like this:

      Structure s = new Structure();
      s.giveDefault();
      s.lengthenTarget(0);
      s.lengthenTarget(0);
      s.addTarget(1);
      s.addPrefix(1);
      s.addSuffix(2);
      s.addPrefix(3);
      s.createTransitions();
      State[] struct = s.getStates();
 

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Serialized Form

Field Summary

static int	BACKGROUND
static int	END
static int	END_STATE
static int	GLOBAL_END
static int	GLOBAL_START
static Double	ONE
static int	PREFIX
protected List	prefixes
static int	START
static int	START_STATE
protected List	stateTypes
static int	SUFFIX
protected List	suffixes
static int	TARGET
protected List	targets
protected List	transitions
static Double	ZERO

Constructor Summary

Structure()

Structure(double[][] transitions, int[] stateTypes)

Structure(State[] states)

Method Summary

void	addPrefix(int length) Legacy method for modifying the structure.
void	addSuffix(int length) Legacy method for modifying the structure.
void	addTarget(int length) Legacy method for modifying the structure.
void	addTransition(int fromState, int toState) Inserts a transition from fromState to toState
static State[]	chrisDefaultStates() Initializes a reasonable default structure, with a background, prefix and suffix states and some number of target states.
static State[]	chrisDefaultStates2() Initializes a reasonable default structure, with a background, prefix and suffix states and some number of target states.
Structure	copy()
static State[]	defaultStates()
List	getIncoming(int toState)
List	getOutgoing(int fromState)
State[]	getStates()
double[][]	getTransitions()
void	giveDefault() Build a simple IE HMM structure, with start and finish state, and one each background, prefix, suffix, and target states.
protected void	giveEmpty()
void	giveErgodic(int[] stateTypes) Builds an ergodic (fully-connected) HMM structure.
void	giveTarget() Build a simple Target HMM structure, with start and finish state and target states only.
void	initializeTransitions() initializes the transition weights in the HMM to "sensible" values
int	insertState(int state, int type) Inserts a new state of given type AFTER the specified state.
static State[]	jimDefaultStates() Initializes a reasonable default structure, with a background, prefix and suffix states and some number of target states.
void	lengthenPrefix(int i) Legacy method for modifying the structure.
void	lengthenSuffix(int i) Legacy method for modifying the structure.
void	lengthenTarget(int i) Legacy method for modifying the structure.
static void	main(String[] args) Provides a sample exercising of the structure creation operations
static Structure	mergeStructures(Structure[] structures)
static void	normalize(double[] dist)
int	numParameters()
int	numPrefixes()
int	numSuffixes()
int	numTargets()
static void	perturbTransitions(double[][] t)
void	setWeight(int fromState, int toState, double weight) Sets the weight for the transition from fromState to toState
int	splitState(int state) Splits a state into two states of the same type producing one new state.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

transitions

protected List transitions

END_STATE

public static final int END_STATE

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Constant Field Values

START_STATE

public static final int START_STATE

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Constant Field Values

GLOBAL_END

public static final int GLOBAL_END

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Constant Field Values

GLOBAL_START

public static final int GLOBAL_START

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Constant Field Values

END

public static final int END

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Constant Field Values

START

public static final int START

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Constant Field Values

BACKGROUND

public static final int BACKGROUND

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Constant Field Values

TARGET

public static final int TARGET

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Constant Field Values

PREFIX

public static final int PREFIX

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Constant Field Values

SUFFIX

public static final int SUFFIX

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Constant Field Values

stateTypes

protected List stateTypes

ONE

public static final Double ONE

ZERO

public static final Double ZERO

prefixes

protected List prefixes

suffixes

protected List suffixes

targets

protected List targets

Constructor Detail

Structure

public Structure()

Structure

public Structure(State[] states)

Structure

public Structure(double[][] transitions,
                 int[] stateTypes)

Method Detail

insertState

public int insertState(int state,
                       int type)

Inserts a new state of given type AFTER the specified state. For example if we had 1->2->(3 4), insertState(2, Structure.SUFFIX) would produce 1->2->5->(3 4). Note that state 2 formerly went to the two states 3 and 4, but now goes instead to the new state 5, and state 5 now goes to 3 and 4. Possible types are Structure.PREFIX, Structure.SUFFIX, Structure.TARGET, and Structure.BACKGROUND

splitState

public int splitState(int state)

Splits a state into two states of the same type producing one new state. For example, if we have 1->2->3, then split(2) produces 1->(2 4)->3. Note that all of the transitions into state 2 also go to the new state 4, and the transitions from state 2 are also in state 4

addTransition

public void addTransition(int fromState,
                          int toState)

Inserts a transition from fromState to toState

setWeight

public void setWeight(int fromState,
                      int toState,
                      double weight)

Sets the weight for the transition from fromState to toState

getOutgoing

public List getOutgoing(int fromState)

Returns:

A List containing the states that can be reached from fromState

getIncoming

public List getIncoming(int toState)

Returns:

A List containing the states that go to toState

giveEmpty

protected void giveEmpty()

giveDefault

public void giveDefault()

Build a simple IE HMM structure, with start and finish state, and one each background, prefix, suffix, and target states.

giveTarget

public void giveTarget()

Build a simple Target HMM structure, with start and finish state and target states only.

giveErgodic

public void giveErgodic(int[] stateTypes)

Builds an ergodic (fully-connected) HMM structure. All states can be reached from any other state except the end state, and all states can go to any other state except the start state. Equal weights are assigned to all transitions, which can be perturbed.

mergeStructures

public static Structure mergeStructures(Structure[] structures)

Returns:

A new structure containing the merged structures

numPrefixes

public int numPrefixes()

numTargets

public int numTargets()

numSuffixes

public int numSuffixes()

addPrefix

public void addPrefix(int length)

Legacy method for modifying the structure. Adds a new prefix chain in the "list of lists" representation. Can only be used if the structure is initialized with @see giveDefault

addSuffix

public void addSuffix(int length)

Legacy method for modifying the structure. Adds a new suffix chain in the "list of lists" representation. Can only be used if the structure is initialized with @see giveDefault

addTarget

public void addTarget(int length)

Legacy method for modifying the structure. Adds a new target chain in the "list of lists" representation. Can only be used if the structure is initialized with @see giveDefault or @see giveTarget

lengthenPrefix

public void lengthenPrefix(int i)

Legacy method for modifying the structure. Extends the named prefix chain in the "list of lists" representation. Can only be used if the structure is initialized with @see giveDefault

lengthenSuffix

public void lengthenSuffix(int i)

Legacy method for modifying the structure. Extends the named suffix chain in the "list of lists" representation. Can only be used if the structure is initialized with @see giveDefault

lengthenTarget

public void lengthenTarget(int i)

Legacy method for modifying the structure. Extends the named target chain chain in the "list of lists" representation. Can only be used if the structure is initialized with @see giveDefault or @see giveTarget

copy

public Structure copy()

initializeTransitions

public void initializeTransitions()

initializes the transition weights in the HMM to "sensible" values

getTransitions

public double[][] getTransitions()

Returns:

The transition matrix for the HMM

perturbTransitions

public static void perturbTransitions(double[][] t)

normalize

public static void normalize(double[] dist)

numParameters

public int numParameters()

getStates

public State[] getStates()

Specified by:

getStates in interface GeneralStructure

toString

public String toString()

Overrides:

toString in class Object

defaultStates

public static State[] defaultStates()

jimDefaultStates

public static State[] jimDefaultStates()

Initializes a reasonable default structure, with a background, prefix and suffix states and some number of target states. The structure is based on a McCallum and Nigam example. We add start, finish, and background states to prefix/suffix/target states.

chrisDefaultStates

public static State[] chrisDefaultStates()

Initializes a reasonable default structure, with a background, prefix and suffix states and some number of target states. The structure is based on a McCallum and Nigam example. We add start, finish, and background states to prefix/suffix/target states. This just changes some transition structure

chrisDefaultStates2

public static State[] chrisDefaultStates2()

Initializes a reasonable default structure, with a background, prefix and suffix states and some number of target states. The structure is based on a McCallum and Nigam example. We add start, finish, and background states to prefix/suffix/target states. Versus the Jim version, this version just changes some transition structure, in hopefully useful ways

main

public static void main(String[] args)

Provides a sample exercising of the structure creation operations