Named Entity Recognizer

Table of contents

About

Stanford NER is a Java implementation of a Named Entity Recognizer. Named Entity Recognition (NER) labels sequences of words in a text which are the names of things, such as person and company names, or gene and protein names. It comes with well-engineered feature extractors for Named Entity Recognition, and many options for defining feature extractors. Included with the download are good named entity recognizers for English, particularly for the 3 classes (PERSON, ORGANIZATION, LOCATION), and we also make available on this page various other models for different languages and circumstances, including models trained on just the CoNLL 2003 English training data.

Stanford NER is also known as CRFClassifier. The software provides a general implementation of (arbitrary order) linear chain Conditional Random Field (CRF) sequence models. That is, by training your own models on labeled data, you can actually use this code to build sequence models for NER or any other task. (CRF models were pioneered by Lafferty, McCallum, and Pereira (2001); see Sutton and McCallum (2006) or Sutton and McCallum (2010) for more comprehensible introductions.)

The original CRF code is by Jenny Finkel. The feature extractors are by Dan Klein, Christopher Manning, and Jenny Finkel. Much of the documentation and usability is due to Anna Rafferty. More recent code development has been done by various Stanford NLP Group members.

Stanford NER is available for download, licensed under the GNU General Public License (v2 or later). Source is included. The package includes components for command-line invocation (look at the shell scripts and batch files included in the download), running as a server (look at NERServer in the sources jar file), and a Java API (look at the simple examples in the [NERDemo.java](https://github.com/stanfordnlp/CoreNLP/blob/main/src/edu/stanford/nlp/ie/demo/NERDemo.java) file included in the download, and then at the javadocs). Stanford NER code is dual licensed (in a similar manner to MySQL, etc.). Open source licensing is under the full GPL, which allows many free uses. For distributors of proprietary software, commercial licensing is available. If you don’t need a commercial license, but would like to support maintenance of these tools, we welcome gifts.

Citation

The CRF sequence models provided here do not precisely correspond to any published paper, but the correct paper to cite for the model and software is:

Jenny Rose Finkel, Trond Grenager, and Christopher Manning. 2005. Incorporating Non-local Information into Information Extraction Systems by Gibbs Sampling. Proceedings of the 43nd Annual Meeting of the Association for Computational Linguistics (ACL 2005), pp. 363-370. http://nlp.stanford.edu/~manning/papers/gibbscrf3.pdf

The software provided here is similar to the baseline local+Viterbi model in that paper, but adds new distributional similarity based features (in the -distSim classifiers). Distributional similarity features improve performance but the models require somewhat more memory. Our big English NER models were trained on a mixture of CoNLL, MUC-6, MUC-7 and ACE named entity corpora, and as a result the models are fairly robust across domains.

Getting started

You can try out Stanford NER CRF classifiers or Stanford NER as part of Stanford CoreNLP on the web, to understand what Stanford NER is and whether it will be useful to you.

To use the software on your computer, download the main CoreNLP package. You then unzip the file by either double-clicking on the zip file, using a program for unpacking zip files, or by using the unzip command. This should create a stanford-corenlp folder. There is no installation procedure, you should be able to run Stanford NER from that folder. Normally, Stanford NER is run from the command line (i.e., shell or terminal). Current releases of Stanford NER require Java 1.8 or later. Either make sure you have or get Java 8 or consider running an earlier version of the software (versions through 3.4.1 support Java 6 and 7)..

NER GUI

Providing java is on your PATH, you should be able to run an NER GUI demonstration by just clicking. It might work to double-click on the stanford- ner.jar archive but this may well fail as the operating system does not give Java enough memory for our NER system, so it is safer to instead double click on the ner-gui.bat icon (Windows) or ner-gui.sh (Linux/Unix/MacOSX). Then, using the top option from the Classifier menu, load a CRF classifier from the classifiers directory of the distribution. You can then either load a text file or web page from the File menu, or decide to use the default text in the window. Finally, you can now named entity tag the text by pressing the Run NER button.

Single CRF NER Classifier from command-line

From a command line, you need to have java on your PATH and the stanford- ner.jar file in your CLASSPATH. (The way of doing this depends on your OS/shell.) The supplied ner.bat and ner.sh should work to allow you to tag a single file, when running from inside the Stanford NER folder. For example, for Windows:

ner <filename>

This corresponds to the full command:

java -mx600m -cp "*;lib\*" edu.stanford.nlp.ie.crf.CRFClassifier -loadClassifier classifiers/english.all.3class.distsim.crf.ser.gz -textFile sample.txt

Or on Unix/Linux you should be able to parse the test file in the distribution directory with the command:

java -mx600m -cp "*:lib/*" edu.stanford.nlp.ie.crf.CRFClassifier -loadClassifier classifiers/english.all.3class.distsim.crf.ser.gz -textFile sample.txt

Here’s an output option that will print out entities and their class to the first two columns of a tab-separated columns output file:

java -mx600m -cp "*;lib/*" edu.stanford.nlp.ie.crf.CRFClassifier -loadClassifier classifiers/english.all.3class.distsim.crf.ser.gz -outputFormat tabbedEntities -textFile sample.txt > sample.tsv

Full Stanford NER functionality

This standalone distribution also allows access to the full NER capabilities of the Stanford CoreNLP pipeline. These capabilities can be accessed via the NERClassifierCombiner class. NERClassifierCombiner allows for multiple CRFs to be used together, and has options for recognizing numeric sequence patterns and time patterns with the rule-based NER of SUTime.

To use NERClassifierCombiner at the command-line, the jars in lib directory and stanford-ner.jar must be in the CLASSPATH. Here is an example command:

java -mx1g -cp "*:lib/*" edu.stanford.nlp.ie.NERClassifierCombiner -textFile sample.txt -ner.model classifiers/english.all.3class.distsim.crf.ser.gz,classifiers/english.conll.4class.distsim.crf.ser.gz,classifiers/english.muc.7class.distsim.crf.ser.gz

The one difference you should see from above is that Sunday is now recognized as a DATE.

Programmatic use via API

You can call Stanford NER from your own code. The file NERDemo.java included in the distribution illustrates several ways of calling the system programatically. We suggest that you start from there, and then look at the javado, etc. as needed.

Programmatic use via a service

Stanford NER can also be set up to run as a server listening on a socket.

Questions

You can look at a Powerpoint Introduction to NER and the Stanford NER package [ppt] [pdf]. There is also a list of Frequently Asked Questions (FAQ), with answers! This includes some information on training models. Further documentation is provided in the included README.txt and in the javadocs.

Feedback and bug reports / fixes can be sent to our mailing lists.

Mailing Lists

We have 3 mailing lists for the Stanford Named Entity Recognizer, all of which are shared with other JavaNLP tools (with the exclusion of the parser). Each address is at @lists.stanford.edu:

1. java-nlp-user This is the best list to post to in order to send feature requests, make announcements, or for discussion among JavaNLP users. (Please ask support questions on Stack Overflow using the stanford-nlp tag.) You have to subscribe to be able to use this list. Join the list via this webpage or by emailing java-nlp-user-join@lists.stanford.edu. (Leave the subject and message body empty.) You can also look at the list archives.

2. java-nlp-announce This list will be used only to announce new versions of Stanford JavaNLP tools. So it will be very low volume (expect 1-3 messages a year). Join the list via this webpage or by emailing java-nlp-announce-join@lists.stanford.edu. (Leave the subject and message body empty.)
3. java-nlp-support This list goes only to the software maintainers. It’s a good address for licensing questions, etc. For general use and support questions, you’re better off joining and usingjava-nlp-user. You cannot join java-nlp-support, but you can mail questions to java-nlp-support@lists.stanford.edu.

Download

The Java NER toolkit is now included in recent distributions of CoreNLP.

There are also previous standalone versions of the NER toolkit:

Download Stanford Named Entity Recognizer version 4.2.0

The download is a 151M zipped file (mainly consisting of classifier data objects). If you unpack that file, you should have everything needed for English NER (or use as a general CRF). It includes batch files for running under Windows or Unix/Linux/MacOSX, a simple GUI, and the ability to run as a server. Stanford NER requires Java v1.8+. If you want to use Stanford NER for other languages, you’ll also need to download model files for those languages; see further below.

Extensions: Packages by others using Stanford NER

For some (computer) languages, there are more up-to-date interfaces to Stanford NER available by using it inside Stanford CoreNLP, and you are better off getting those from the CoreNLP page and using them….

• Apache Tika: Named Entity Recognition (NER) with Tika.
• JavaScript/npm:
  • Pranav Herur has written ner-server. Source on github.
  • Nikhil Srivastava has written ner. Source on github.
  • Varun Chatterji has written stanford-ner. Source on github.
• .NET/F#/C#: Sergey Tihon has ported Stanford NER to F# (and other .NET languages, such as C#), using IKVM. See also pages on: GitHub and NuGet.
• Perl: Kieren Diment has written Text-NLP-Stanford-EntityExtract, a Perl module that provides an interface to Stanford NER running as a server.
• PHP: Patrick Schur in 2017 wrote PHP wrapper for Stanford POS and NER taggers. Also on packagist. Second choice: PHP-Stanford-NLP. Supports POS Tagger, NER, Parser. By Anthony Gentile (agentile).
• Python:
  • Dat Hoang wrote pyner, a Python interface to Stanford NER. [Old version.]
  • NLTK (2.0+) contains an interface to Stanford NER written by Nitin Madnani: documentation (note: set the character encoding or you get ASCII by default!), code, on Github.
  • scrapy-corenlp, a Python Scrapy (web page scraping) middleware by Jithesh E. J. PyPI.
• Ruby: tiendung has written a Ruby Binding for the Stanford POS tagger and Named Entity Recognizer.
• UIMA: Florian Laws made a Stanford NER UIMA annotator using a modified version of Stanford NER, which is available on his homepage. [Old version.]

Models

Included with Stanford NER are a 4 class model trained on the CoNLL 2003 eng.train, a 7 class model trained on the MUC 6 and MUC 7 training data sets, and a 3 class model trained on both data sets and some additional data (including ACE 2002 and limited amounts of in-house data) on the intersection of those class sets. (The training data for the 3 class model does not include any material from the CoNLL eng.testa or eng.testb data sets, nor any of the MUC 6 or 7 test or devtest datasets, nor Alan Ritter’s Twitter NER data, so all of these remain valid tests of its performance.)

These models each use distributional similarity features, which provide considerable performance gain at the cost of increasing their size and runtime. We also have models that are the same except without the distributional similarity features. You can find them in our English models jar. You can either unpack the jar file or add it to the classpath; if you add the jar file to the classpath, you can then load the models from the path edu/stanford/nlp/models/.... You can run jar -tf <jar-file> to get the list of files in the jar file.

Also available are caseless versions of these models, better for use on texts that are mainly lower or upper case, rather than follow the conventions of standard English

Important note: There was a problem with the v3.6.0 English Caseless NER model. See this page.

German

A German NER model is available, based on work by Manaal Faruqui and Sebastian Padó. You can find it in the CoreNLP German models jar. For citation and other information relating to the German classifiers, please see Sebastian Pado’s German NER page (but the models there are now many years old; you should use the better models that we have!). It is a 4 class IOB1 classifier (see, e.g., Memory-Based Shallow Parsing by Erik F. Tjong Kim Sang). The tags given to words are: I-LOC, I-PER, I-ORG, I-MISC, B-LOC, B-PER, B-ORG, B-MISC, O. It is trained over the CoNLL 2003 data with distributional similarity classes built from the Huge German Corpus.

German resources (written in German): a help page for Stanford NER; a workshop on using Stanford CoreNLP for NER with materials available.

Here are a couple of commands using these models, two sample files, and a couple of notes. Running on TSV files: the models were saved with options for testing on German CoNLL NER files. While the models use just the surface word form, the input reader expects the word in the first column and the class in the fifth colum (1-indexed colums). You can either make the input like that or else change the expectations with, say, the option -map "word=0,answer=1" (0-indexed columns). These models were also trained on data with straight ASCII quotes and BIO entity tags. Also, be careful of the text encoding: The default is Unicode; use -encoding iso-8859-15 if the text is in 8-bit encoding.

TSV mini test file: german-ner.tsv — Text mini test file: german-ner.txt

java -cp "*" edu.stanford.nlp.ie.crf.CRFClassifier -loadClassifier edu/stanford/nlp/models/ner/german.conll.hgc_175m_600.crf.ser.gz -testFile german-ner.tsv
java -cp "*" edu.stanford.nlp.ie.crf.CRFClassifier -loadClassifier edu/stanford/nlp/models/ner/german.conll.hgc_175m_600.crf.ser.gz -tokenizerOptions latexQuotes=false -textFile german-ner.txt

Spanish

From version 3.4.1 forward, we have a Spanish model available for NER. It is included in the Spanish corenlp models jar.

Chinese

We also provide Chinese models built from the Ontonotes Chinese named entity data. There are two models, one using distributional similarity clusters and one without. These are designed to be run on word-segmented Chinese. So, if you want to use these on normal Chinese text, you will first need to run Stanford Word Segmenter or some other Chinese word segmenter, and then run NER on the output of that!

Online Demo

We have an online demo of several of our NER models. Special thanks to Dat Hoang, who provided the initial version. Note that the online demo demonstrates single CRF models; in order to see the effect of the time annotator or the combined models, see CoreNLP.

Release History