- All Implemented Interfaces:
public class TextProfileSignature
- extends Signature
An implementation of a page signature. It calculates an MD5 hash
of a plain text "profile" of a page. In case there is no text, it
calculates a hash using the
The algorithm to calculate a page "profile" takes the plain text version of
a page and performs the following steps:
This list is then submitted to an MD5 hash calculation.
- remove all characters except letters and digits, and bring all characters
to lower case,
- split the text into tokens (all consecutive non-whitespace characters),
- discard tokens equal or shorter than MIN_TOKEN_LEN (default 2 characters),
- sort the list of tokens by decreasing frequency,
- round down the counts of tokens to the nearest multiple of QUANT
QUANT = QUANT_RATE * maxFreq, where
QUANT_RATE is 0.01f
by default, and
maxFreq is the maximum token frequency). If
maxFreq is higher than 1, then QUANT is always higher than 2 (which
means that tokens with frequency 1 are always discarded).
- tokens, which frequency after quantization falls below QUANT, are discarded.
- create a list of tokens and their quantized frequency, separated by spaces,
in the order of decreasing frequency.
- Andrzej Bialecki <email@example.com>
|Fields inherited from class org.apache.nutch.crawl.Signature
|Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
public byte calculate(Content content,
- Specified by:
calculate in class
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