Using OpenNLP with Solr to improve search relevance and to extract named entities
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Apache OpenNLP can be used with Lucene and Solr to tag words with part-of-speech, produce lemmas (words’ base forms), and to extract named entities: people, places, organizations, etc.
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Using OpenNLP with Solr to improve search relevance and to extract named entities
- 1. Using OpenNLP with Solr to improve search relevance and to extract named entities Steve Rowe Lucidworks
- 2. About me • Previously worked at the Center for Natural Language Processing at Syracuse University • Sr. Software Engineer at Lucidworks • Committer on Apache Lucene/Solr project • Committer on JFlex scanner generator project
- 3. Apache OpenNLP • sentence segmentation • tokenization • part-of-speech tagging • lemmatization • named entity extraction • phrase chunking • parsing • coreference resolution • machine learning: maximum entropy and perceptron based • caveat: model licensing: not Apache
- 4. Expectation Management • OpenNLP isn’t integrated with Solr in any release • LUCENE-2899: patches • TDD (talk driven development) • No Spanish - OpenNLP doesn’t publish Spanish models for sentence splitting, tokenization, or part- of-speech. • No precision/recall/F-measure/MAP testing
- 5. LUCENE-2899 • Created: 30/Jan/11 10:44 <- over 5 years old • Lance Norskog wrote the bulk of the implementation • I modernized Lance’s patch and added lemmatization support
- 6. Lemmatization vs. stemming • Both can be used with search to increase recall • Lemmas are real words: infinitive verbs, singular nouns • e.g. Speaking/VBG, spoke/VB -> speak; stigmata/NNS -> stigma • Can be produced by algorithm and/or known-item dictionary • OpenNLP 1.6.1 will include a machine-learned lemmatization implementation • Caveat: poor quality part-of-speech over short query text • Stems are not (necessarily) real words • e.g. Speaking -> speak, spoke -> spoke, stigmata -> stigmata (Porter stemmer) • produced via algorithm
- 7. Penn Treebank part of speech tags https://www.ling.upenn.edu/courses/Fall_2003/ling001/penn_treebank_pos.html CC Coordinating conjunction CD Cardinal number DT Determiner EX Existential there FW Foreign word IN Preposition/subordinating conjunction JJ Adjective JJR Adjective, comparative JJS Adjective, superlative LS List item marker MD Modal NN Noun, singular or mass NNS Noun, plural NNP Proper noun, singular NNPS Proper noun, plural PDT Predeterminer POS Possessive ending PRP Personal pronoun PRP$ Possessive pronoun RB Adverb RBR Adverb, comparative RBS Adverb, superlative RP Particle SYM Symbol TO to UH Interjection VB Verb, base form VBD Verb, past tense VBG Verb, gerund or present participle VBN Verb, past participle VBP Verb, non-3rd person singular present VBZ Verb, 3rd person singular present WDT Wh-determiner WP Wh-pronoun WP$ Possessive wh-pronoun WRB Wh-adverb
- 8. Solr OpenNLP integration • Put jars on classpath • Add required resources to configset: • models • lemmatization dictionary • Add field type(s) using OpenNLP-based analysis components, then fields using these field types
- 9. Put jars on classpath • Add to configset’s solrconfig.xml: <lib dir="${solr.install.dir:../../../..} /contrib/analysis-extras/lucene-libs" regex=".*.jar" /> <lib dir="${solr.install.dir:../../../..} /contrib/analysis-extras/lib" regex="opennlp-.*.jar"/>
- 10. Add required resources to configset • Download models from http://opennlp.sourceforge.net/models-1.5/ • Download lemma dictionary from http://ixa2.si.ehu.es/ragerri/lemmatizer-dicts.tgz conf/ opennlp/ en-ner-person.bin en-pos-maxent.bin en-sent.bin en-token.bin language-tool-en-lemmatizer.txt
- 11. Add field types and fields curl -X POST http://localhost:8983/solr/opennlp/schema -H 'Content-type: application/json' --data-binary '{ "add-field-type":{ "name":"text_lemma", "class":"solr.TextField", "positionIncrementGap":"100", "analyzer":{ "tokenizer":{ "class":"solr.OpenNLPTokenizerFactory", "sentenceModel":"opennlp/en-sent.bin", "tokenizerModel":"opennlp/en-token.bin" }, "filters":[{ "class":"solr.OpenNLPFilterFactory", "posTaggerModel":"opennlp/en-pos-maxent.bin" },{ "class":"solr.OpenNLPLemmatizerFilterFactory", "dictionary":"opennlp/language-tool-en-lemmatizer.txt" }]}}, "add-field":{ "name":"content_lemma", "type":"text_lemma", “stored":true } }'
- 12. Next steps • Switch tags from payloads to token “type” attribute • Make Solr update request processors for named entity extraction, maybe phrase chunker • Commit/release LUCENE-2899!