org.basex.query.ft
Class Scoring

java.lang.Object
  org.basex.query.ft.Scoring

public final class Scoring
extends Object

Simple default scoring model, assembling all scoring calculations.

Author:

Workgroup DBIS, University of Konstanz 2005-10, ISC License, Christian Gruen

Field Summary

static int

MP Scoring multiplier to store values as integers.

Constructor Summary

Scoring()

Method Summary

double	and(double o, double n) Combines two scoring values.
double	let(double s, int c) Returns a score for the let clause.
double	not(double d) Inverses the scoring value for FTNot.
double	or(double o, double n) Combines two scoring values.
static double	phrase(double w1, double w2) Returns the scoring value for a phrase.
static double	step(double sc) Returns a score for a single step.
static double	textNode(double npv, double is, double tokl, double tl) Returns the score for a text node.
static int	tfIDF(double freq, double mfreq, double docs, double tokens) Returns a tf-idf for the specified values.
static double	union(double w1, double w2) Returns the union value.
double	word(int tl, double l) Calculates a score value, based on the token length and complete text length.

Methods inherited from class java.lang.Object

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

Field Detail

MP

public static final int MP

Scoring multiplier to store values as integers.

See Also:

Constant Field Values

Constructor Detail

Scoring

public Scoring()

Method Detail

word

public double word(int tl,
                   double l)

Calculates a score value, based on the token length and complete text length.

Parameters:

tl - token length

l - complete length

Returns:

result

and

public double and(double o,
                  double n)

Combines two scoring values.

Parameters:

o - old value

n - new value

Returns:

result

or

public double or(double o,
                 double n)

Combines two scoring values.

Parameters:

o - old value

n - new value

Returns:

result

not

public double not(double d)

Inverses the scoring value for FTNot.

Parameters:

d - scoring value

Returns:

inverse scoring value

let

public double let(double s,
                  int c)

Returns a score for the let clause.

Parameters:

s - summed up scoring values

c - number of values

Returns:

new score value

tfIDF

public static int tfIDF(double freq,
                        double mfreq,
                        double docs,
                        double tokens)

Returns a tf-idf for the specified values. Used definition: freq(i, j) / max(l, freq(l, j)) * log(1 + N / n(i)). The result is multiplied with the MP constant to yield integer values. The value 2 is used as minimum score, as the total minimum value will be subtracted by 1 to avoid eventual 0 scores.

Parameters:

freq - frequency of the token. TF: freq(i, j)

mfreq - maximum occurrence of a token. TF: max(l, freq(l, j))

docs - number of documents in the collection. IDF: N

tokens - number of documents containing the token. IDF: n(i)

Returns:

score value

textNode

public static double textNode(double npv,
                              double is,
                              double tokl,
                              double tl)

Returns the score for a text node. Used when no index score is available.

Parameters:

npv - number of pos values

is - index size

tokl - token length

tl - text length

Returns:

score value

phrase

public static double phrase(double w1,
                            double w2)

Returns the scoring value for a phrase.

Parameters:

w1 - score of word1

w2 - score of word2

Returns:

score of the phrase

union

public static double union(double w1,
                           double w2)

Returns the union value.

Parameters:

w1 - score of word1

w2 - score of word2

Returns:

score of the phrase

step

public static double step(double sc)

Returns a score for a single step.

Parameters:

sc - current score value

Returns:

new score value