com.pervasive.datarush.matching.functions

Class Similarity

java.lang.Object

com.pervasive.datarush.matching.functions.Similarity

public class Similarity
extends Object

A collection of functions for computing similarity of strings. These functions are used to perform "fuzzy" matches between values, attempting to account for common entry errors or other equivalences.

These functions return a floating point value normalized to the range [0,1] with 0 representing no similarity at all and 1 representing an exact match. Null valued inputs are considered totally dissimilar to any other string (including the null value) and will always return 0.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_MAX_DISTANCE The default maximum distance for the positional q-gram measure.
static int	DEFAULT_PREFIX_LENGTH The default prefix length for the Jaro-Winkler measure.
static int	DEFAULT_Q The default q-gram size for the q-gram and positional q-gram measures.
static float	DEFAULT_SCALING_FACTOR The default scaling factor for the Jaro-Winkler measure.
static String	PROP_MAX_DISTANCE Name of the property specifying maximum distance for the positional q-gram measure.
static String	PROP_PREFIX_LENGTH Name of the property specifying prefix length for the Jaro-Winkler measure.
static String	PROP_Q Name of the property specifying the q-gram size for the q-gram and positional q-gram measures.
static String	PROP_SCALING_FACTOR Name of the property specifying scaling factor for the Jaro-Winkler measure.

Constructor Summary

Constructors

Constructor and Description
Similarity()

Method Summary

Modifier and Type	Method and Description
static ScalarValuedFunction	contains(ScalarValuedFunction left, ScalarValuedFunction right) Builds a function testing whether either of the specified string valued expressions contains the other.
static ScalarValuedFunction	contains(String left, String right) Builds a function testing whether either of the specified fields has a string value containing the other.
static ScalarValuedFunction	damerauLevenshtein(ScalarValuedFunction left, ScalarValuedFunction right) Builds a function computing the Damerau-Levenshtein distance between the specified string valued expressions.
static ScalarValuedFunction	damerauLevenshtein(String left, String right) Builds a function computing the Damerau-Levenshtein distance between the string values of the specified fields.
static ScalarValuedFunction	exact(ScalarValuedFunction left, ScalarValuedFunction right) Builds a function testing whether the specified string valued expressions are equal.
static ScalarValuedFunction	exact(String left, String right) Builds a function testing exact equality between the string values of the specified fields.
static ScalarValuedFunction	jaro(ScalarValuedFunction left, ScalarValuedFunction right) Builds a function computing the Jaro distance between the specified string valued expressions.
static ScalarValuedFunction	jaro(String left, String right) Builds a function computing the Jaro distance between the specified string valued expressions.
static ScalarValuedFunction	jaroWinkler(ScalarValuedFunction left, ScalarValuedFunction right, int prefixLen, float scaling) Builds a function computing the Jaro-Winkler distance between the specified string valued expressions.
static ScalarValuedFunction	jaroWinkler(String left, String right, int prefixLen, float scaling) Builds a function computing the Jaro-Winkler distance between the specified string valued expressions.
static ScalarValuedFunction	levenshtein(ScalarValuedFunction left, ScalarValuedFunction right) Builds a function computing the Levenshtein distance between the specified string valued expressions.
static ScalarValuedFunction	levenshtein(String left, String right) Builds a function computing the Levenshtein distance between the string values of the specified fields.
static ScalarValuedFunction	positionalQgram(ScalarValuedFunction left, ScalarValuedFunction right, int q, int maxDist) Builds a function computing the percentage of q-grams in common between the specified string valued expressions.
static ScalarValuedFunction	positionalQgram(String left, String right, int q, int maxDist) Builds a function computing the percentage of q-grams in common between the string values of the specified fields.
static ScalarValuedFunction	proximity(ScalarValuedFunction left, ScalarValuedFunction right) Builds a function computing an adjusted quotient of the numeric values of the specified fields.
static ScalarValuedFunction	proximity(String left, String right) Builds a function computing an adjusted quotient of the numeric values of the specified fields.
static ScalarValuedFunction	qgram(ScalarValuedFunction left, ScalarValuedFunction right, int q) Builds a function computing the percentage of q-grams in common between the specified string valued expressions.
static ScalarValuedFunction	qgram(String left, String right, int q) Builds a function computing the percentage of q-grams in common between the string values of the specified fields.
static ScalarValuedFunction	shorthand(ScalarValuedFunction left, ScalarValuedFunction right) Builds a function testing shorthand equivalence between the specified string valued expressions.
static ScalarValuedFunction	shorthand(String left, String right) Builds a function testing shorthand equivalence between the string values of the specified fields.

Methods inherited from class java.lang.Object

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

Field Detail

PROP_Q

public static final String PROP_Q

Name of the property specifying the q-gram size for the q-gram and positional q-gram measures.

See Also:

Constant Field Values

DEFAULT_Q

public static final int DEFAULT_Q

The default q-gram size for the q-gram and positional q-gram measures.

See Also:

Constant Field Values

PROP_MAX_DISTANCE

public static final String PROP_MAX_DISTANCE

Name of the property specifying maximum distance for the positional q-gram measure.

See Also:

Constant Field Values

DEFAULT_MAX_DISTANCE

public static final int DEFAULT_MAX_DISTANCE

The default maximum distance for the positional q-gram measure.

See Also:

Constant Field Values

PROP_PREFIX_LENGTH

public static final String PROP_PREFIX_LENGTH

Name of the property specifying prefix length for the Jaro-Winkler measure.

See Also:

Constant Field Values

PROP_SCALING_FACTOR

public static final String PROP_SCALING_FACTOR

Name of the property specifying scaling factor for the Jaro-Winkler measure.

See Also:

Constant Field Values

DEFAULT_PREFIX_LENGTH

public static final int DEFAULT_PREFIX_LENGTH

The default prefix length for the Jaro-Winkler measure.

See Also:

Constant Field Values

DEFAULT_SCALING_FACTOR

public static final float DEFAULT_SCALING_FACTOR

The default scaling factor for the Jaro-Winkler measure.

See Also:

Constant Field Values

Constructor Detail

Similarity

public Similarity()

Method Detail

contains

public static ScalarValuedFunction contains(String left,
                                            String right)

Builds a function testing whether either of the specified fields has a string value containing the other. This function returns 1 if one value is contained in the other, 0 if not.

Parameters:

left - the first record field

right - the second record field

Returns:

the specified function

contains

public static ScalarValuedFunction contains(ScalarValuedFunction left,
                                            ScalarValuedFunction right)

Builds a function testing whether either of the specified string valued expressions contains the other. This function returns 1 if one value is contained in the other, 0 if not.

Parameters:

left - the first string valued expression

right - the second string valued expression

Returns:

the specified function

damerauLevenshtein

public static ScalarValuedFunction damerauLevenshtein(String left,
                                                      String right)

Builds a function computing the Damerau-Levenshtein distance between the string values of the specified fields. This value is normalized to the range 0 to 1 (inclusive) by dividing by the length of the longer input string.

Parameters:

left - the first record field

right - the second record field

Returns:

the specified function

damerauLevenshtein

public static ScalarValuedFunction damerauLevenshtein(ScalarValuedFunction left,
                                                      ScalarValuedFunction right)

Builds a function computing the Damerau-Levenshtein distance between the specified string valued expressions. This value is normalized to the range 0 to 1 (inclusive) by dividing by the length of the longer input string.

Parameters:

left - the first string valued expression

right - the second string valued expression

Returns:

the specified function

exact

public static ScalarValuedFunction exact(String left,
                                         String right)

Builds a function testing exact equality between the string values of the specified fields. This function returns 1 if the values are equal, 0 if not.

Parameters:

left - the first record field

right - the second record field

Returns:

the specified function

exact

public static ScalarValuedFunction exact(ScalarValuedFunction left,
                                         ScalarValuedFunction right)

Builds a function testing whether the specified string valued expressions are equal. This function returns 1 if the values are equal, 0 if not.

Parameters:

left - the first string valued expression

right - the second string valued expression

Returns:

the specified function

jaro

public static ScalarValuedFunction jaro(String left,
                                        String right)

Builds a function computing the Jaro distance between the specified string valued expressions.

Parameters:

left - the first string valued expression

right - the second string valued expression

Returns:

the specified function

jaro

public static ScalarValuedFunction jaro(ScalarValuedFunction left,
                                        ScalarValuedFunction right)

Builds a function computing the Jaro distance between the specified string valued expressions.

Parameters:

left - the first string valued expression

right - the second string valued expression

Returns:

the specified function

jaroWinkler

public static ScalarValuedFunction jaroWinkler(String left,
                                               String right,
                                               int prefixLen,
                                               float scaling)

Builds a function computing the Jaro-Winkler distance between the specified string valued expressions.

Parameters:

left - the first string valued expression

right - the second string valued expression

prefixLen - the maximum length of the common prefix for score adjustment purposes

scaling - the scaling factor for scoring common prefixes

Returns:

the specified function

jaroWinkler

public static ScalarValuedFunction jaroWinkler(ScalarValuedFunction left,
                                               ScalarValuedFunction right,
                                               int prefixLen,
                                               float scaling)

Builds a function computing the Jaro-Winkler distance between the specified string valued expressions.

Parameters:

left - the first string valued expression

right - the second string valued expression

prefixLen - the maximum length of the common prefix for score adjustment purposes

scaling - the scaling factor for scoring common prefixes

Returns:

the specified function

levenshtein

public static ScalarValuedFunction levenshtein(String left,
                                               String right)

Builds a function computing the Levenshtein distance between the string values of the specified fields. This value is normalized to the range 0 to 1 (inclusive) by dividing by the length of the longer input string.

Parameters:

left - the first record field

right - the second record field

Returns:

the specified function

levenshtein

public static ScalarValuedFunction levenshtein(ScalarValuedFunction left,
                                               ScalarValuedFunction right)

Builds a function computing the Levenshtein distance between the specified string valued expressions. This value is normalized to the range 0 to 1 (inclusive) by dividing by the length of the longer input string.

Parameters:

left - the first string valued expression

right - the second string valued expression

Returns:

the specified function

qgram

public static ScalarValuedFunction qgram(String left,
                                         String right,
                                         int q)

Builds a function computing the percentage of q-grams in common between the string values of the specified fields. This is the count of q-grams in common divided by the number of possible q-grams in the longer string.

Parameters:

left - the first record field

right - the second record field

q - the size of q-grams to compare

Returns:

the specified function

qgram

public static ScalarValuedFunction qgram(ScalarValuedFunction left,
                                         ScalarValuedFunction right,
                                         int q)

Builds a function computing the percentage of q-grams in common between the specified string valued expressions. This is the count of q-grams in common divided by the number of possible q-grams in the longer string.

Parameters:

left - the first string valued expression

right - the second string valued expression

q - the size of q-grams to compare

Returns:

the specified function

positionalQgram

public static ScalarValuedFunction positionalQgram(String left,
                                                   String right,
                                                   int q,
                                                   int maxDist)

Builds a function computing the percentage of q-grams in common between the string values of the specified fields. Q-grams are only counted as common if they appear near the position they appear in the longer string. The resulting count is then divided by the number of possible q-grams in the longer string.

Parameters:

left - the first record field

right - the second record field

q - the size of q-grams to compare

maxDist - the maximum distance, in characters, a q-gram can be from its original position

Returns:

the specified function

positionalQgram

public static ScalarValuedFunction positionalQgram(ScalarValuedFunction left,
                                                   ScalarValuedFunction right,
                                                   int q,
                                                   int maxDist)

Builds a function computing the percentage of q-grams in common between the specified string valued expressions. Q-grams are only counted as common if they appear near the position they appear in the longer string. The resulting count is then divided by the number of possible q-grams in the longer string.

Parameters:

left - the first string valued expression

right - the second string valued expression

q - the size of q-grams to compare

maxDist - the maximum distance, in characters, a q-gram can be from its original position

Returns:

the specified function

shorthand

public static ScalarValuedFunction shorthand(String left,
                                             String right)

Builds a function testing shorthand equivalence between the string values of the specified fields. This function returns 1 if the shorter value is a shorthand representation of the longer value, 0 if not. To be a shorthand representation, the all characters in the shorter string must appear in the longer in the same order. Additionally, if the longer contains multiple words, a letter can only match if at least the first letter of the word was matched also. For example, "ABC" would not match "Acme SoftBall Corporation" since the 'S' starting "SoftBall" doesn't match, therefore the 'B' doesn't count as a match. However, "Acme Soft Ball Corporation" does match, as the 'B' starts a word.

Parameters:

left - the first record field

right - the second record field

Returns:

the specified function

shorthand

public static ScalarValuedFunction shorthand(ScalarValuedFunction left,
                                             ScalarValuedFunction right)

Builds a function testing shorthand equivalence between the specified string valued expressions. This function returns 1 if the shorter value is a shorthand representation of the longer value, 0 if not. To be a shorthand representation, the all characters in the shorter string must appear in the longer in the same order. Additionally, if the longer contains multiple words, a letter can only match if at least the first letter of the word was matched also. For example, "ABC" would not match "Acme SoftBall Corporation" since the 'S' starting "SoftBall" doesn't match, therefore the 'B' doesn't count as a match. However, "Acme Soft Ball Corporation" does match, as the 'B' starts a word.

Parameters:

left - the first string valued expression

right - the second string valued expression

Returns:

the specified function

proximity

public static ScalarValuedFunction proximity(String left,
                                             String right)

Builds a function computing an adjusted quotient of the numeric values of the specified fields. The result is the smaller number divided by the larger. If either value is zero (excepting if both are zero) or if the signs differ, 0 is returned.

Parameters:

left - the first record field

right - the second record field

Returns:

the specified function

proximity

public static ScalarValuedFunction proximity(ScalarValuedFunction left,
                                             ScalarValuedFunction right)

Builds a function computing an adjusted quotient of the numeric values of the specified fields. The result is the smaller number divided by the larger. If either value is zero (excepting if both are zero) or if the signs differ, 0 is returned.

Parameters:

left - the first string valued expression

right - the second string valued expression

Returns:

the specified function