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https://issues.apache.org/jira/browse/LUCENE-826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12804285#action_12804285
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Ken Krugler commented on LUCENE-826:
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I think Nutch (and eventually Mahout) plan to use Tika for
charset/mime-type/language detection going forward.
I've filed an issue [TIKA-369] about improving the current Tika code, which is
a simplification of the Nutch code. While using this on lots of docs, there
were performance issues. And for small chunks of text the quality isn't very
good.
It would be interesting if Karl could comment on the approach Ted Dunning took
(many years ago - 1994 :)) versus what he did.
> Language detector
> -----------------
>
> Key: LUCENE-826
> URL: https://issues.apache.org/jira/browse/LUCENE-826
> Project: Lucene - Java
> Issue Type: New Feature
> Reporter: Karl Wettin
> Assignee: Karl Wettin
> Attachments: ld.tar.gz, ld.tar.gz
>
>
> A formula 1A token/ngram-based language detector. Requires a paragraph of
> text to avoid false positive classifications.
> Depends on contrib/analyzers/ngrams for tokenization, Weka for classification
> (logistic support vector models) feature selection and normalization of token
> freuencies. Optionally Wikipedia and NekoHTML for training data harvesting.
> Initialized like this:
> {code}
> LanguageRoot root = new LanguageRoot(new
> File("documentClassifier/language root"));
> root.addBranch("uralic");
> root.addBranch("fino-ugric", "uralic");
> root.addBranch("ugric", "uralic");
> root.addLanguage("fino-ugric", "fin", "finnish", "fi", "Suomi");
> root.addBranch("proto-indo european");
> root.addBranch("germanic", "proto-indo european");
> root.addBranch("northern germanic", "germanic");
> root.addLanguage("northern germanic", "dan", "danish", "da", "Danmark");
> root.addLanguage("northern germanic", "nor", "norwegian", "no", "Norge");
> root.addLanguage("northern germanic", "swe", "swedish", "sv", "Sverige");
> root.addBranch("west germanic", "germanic");
> root.addLanguage("west germanic", "eng", "english", "en", "UK");
> root.mkdirs();
> LanguageClassifier classifier = new LanguageClassifier(root);
> if (!new File(root.getDataPath(), "trainingData.arff").exists()) {
> classifier.compileTrainingData(); // from wikipedia
> }
> classifier.buildClassifier();
> {code}
> Training set build from Wikipedia is the pages describing the home country of
> each registred language in the language to train. Above example pass this
> test:
> (testEquals is the same as assertEquals, just not required. Only one of them
> fail, see comment.)
> {code}
> assertEquals("swe", classifier.classify(sweden_in_swedish).getISO());
> testEquals("swe", classifier.classify(norway_in_swedish).getISO());
> testEquals("swe", classifier.classify(denmark_in_swedish).getISO());
> testEquals("swe", classifier.classify(finland_in_swedish).getISO());
> testEquals("swe", classifier.classify(uk_in_swedish).getISO());
> testEquals("nor", classifier.classify(sweden_in_norwegian).getISO());
> assertEquals("nor", classifier.classify(norway_in_norwegian).getISO());
> testEquals("nor", classifier.classify(denmark_in_norwegian).getISO());
> testEquals("nor", classifier.classify(finland_in_norwegian).getISO());
> testEquals("nor", classifier.classify(uk_in_norwegian).getISO());
> testEquals("fin", classifier.classify(sweden_in_finnish).getISO());
> testEquals("fin", classifier.classify(norway_in_finnish).getISO());
> testEquals("fin", classifier.classify(denmark_in_finnish).getISO());
> assertEquals("fin", classifier.classify(finland_in_finnish).getISO());
> testEquals("fin", classifier.classify(uk_in_finnish).getISO());
> testEquals("dan", classifier.classify(sweden_in_danish).getISO());
> // it is ok that this fails. dan and nor are very similar, and the
> document about norway in danish is very small.
> testEquals("dan", classifier.classify(norway_in_danish).getISO());
> assertEquals("dan", classifier.classify(denmark_in_danish).getISO());
> testEquals("dan", classifier.classify(finland_in_danish).getISO());
> testEquals("dan", classifier.classify(uk_in_danish).getISO());
> testEquals("eng", classifier.classify(sweden_in_english).getISO());
> testEquals("eng", classifier.classify(norway_in_english).getISO());
> testEquals("eng", classifier.classify(denmark_in_english).getISO());
> testEquals("eng", classifier.classify(finland_in_english).getISO());
> assertEquals("eng", classifier.classify(uk_in_english).getISO());
> {code}
> I don't know how well it works on lots of lanugages, but this fits my needs
> for now. I'll try do more work on considering the language trees when
> classifying.
> It takes a bit of time and RAM to build the training data, so the patch
> contains a pre-compiled arff-file.
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