Recognizes named entities (person and company names, etc.) in text.
Principally, this annotator uses one or more machine learning sequence
models to label entities, but it may also call specialist rule-based
components, such as for labeling and interpreting times and dates.
Numerical entities that require normalization, e.g., dates,
have their normalized value stored in NormalizedNamedEntityTagAnnotation.
For more extensive support for rule-based NER, you may also want to
look at the RegexNER annotator.
The set of entities recognized is language-dependent, and the
recognized set of entities is frequently more limited for other
languages than what is
described below for English. As the name “NERClassifierCombiner”
implies, commonly this annotator will run several named entity
recognizers and then combine their results but it can run just a
single annotator or only rule-based quantity NER.
For English, by default, this annotator recognizes
named (PERSON, LOCATION, ORGANIZATION, MISC), numerical (MONEY,
NUMBER, ORDINAL, PERCENT), and temporal (DATE, TIME, DURATION, SET)
entities (12 classes). Adding the
regexner annotator and using the supplied RegexNER pattern
files adds support for the fine-grained and additional entity classes
EMAIL, URL, CITY, STATE_OR_PROVINCE, COUNTRY, NATIONALITY, RELIGION,
(job) TITLE, IDEOLOGY, CRIMINAL_CHARGE, CAUSE_OF_DEATH (11 classes)
for a total of 23 classes. Named entities are recognized using a combination of three
CRF sequence taggers trained on various corpora, including CoNLL, ACE,
MUC, and ERE corpora. Numerical entities are recognized using a rule-based
||Annotator class name
||NamedEntityTagAnnotation and NormalizedNamedEntityTagAnnotation
||A comma-separated list of NER model names (or just a single name is okay). If none are specified, a default list of English models is used (3class, 7class, and MISCclass, in that order). The names will be looked for as classpath resources, filenames, or URLs.
||Whether or not to use numeric classifiers, for money, percent, numbers, including SUTime. These are hardcoded for English, so if using a different language, this should be set to false.
||Whether or not to use SUTime. SUTime at present only supports English; if not processing English, make sure to set this to false.
||Tells SUTime whether to mark phrases such as “From January to March” as a range, instead of marking “January” and “March” separately.
||If marking time ranges, set the time range in the TIMEX output from SUTime.
||Limit the size of the known lower case words set. Set this to 0 to prevent ordering issues (i.e. when this is nonzero running on document1 then document2 can have different results than running on document2 then document1
StanfordCoreNLP includes SUTime, Stanford’s temporal expression
recognizer. SUTime is transparently called from the “ner” annotator,
so no configuration is necessary. Furthermore, the “cleanxml”
annotator can extract the reference date for a given XML document, so
relative dates, e.g., “yesterday”, are transparently normalized with
no configuration necessary.
SUTime supports the same annotations as before, i.e.,
NamedEntityTagAnnotation is set with the label of the numeric entity (DATE,
TIME, DURATION, MONEY, PERCENT, or NUMBER) and
NormalizedNamedEntityTagAnnotation is set to the value of the normalized
temporal expression. Note that NormalizedNamedEntityTagAnnotation now
follows the TIMEX3 standard, rather than Stanford’s internal representation,
e.g., “2010-01-01” for the string “January 1, 2010”, rather than “20100101”.
Also, SUTime now sets the TimexAnnotation key to an
edu.stanford.nlp.time.Timex object, which contains the complete list of
TIMEX3 fields for the corresponding expressions, such as “val”, “alt_val”,
“type”, “tid”. This might be useful to developers interested in recovering
complete TIMEX3 expressions.
Reference dates are by default extracted from the “datetime” and
“date” tags in an xml document. To set a different set of tags to
use, use the clean.datetags property. When using the API, reference
dates can be added to an
although note that when processing an xml document, the cleanxml
annotator will overwrite the
“datetime” or “date” are specified in the document.
It is possible to run StanfordCoreNLP with NER
models that ignore capitalization. We have trained models like this
for English. You can find details on the
Caseless models page.
Training or retraining new models
The train/dev/test data files should be in the following format:
In this example, each line is a token, followed by a tab, followed by the NER tag. A blank line represents a sentence break.
The model that we release is trained on over a million tokens. The more training data you have, the more accurate your model should be.
The standard training data sets used for PERSON/LOCATION/ORGANIZATION/MISC must be purchased from the LDC, we do not distribute them.
Here is the command for starting the training process (make sure your CLASSPATH is set up to include all of the Stanford CoreNLP jars):
java -Xmx2g edu.stanford.nlp.ie.crf.CRFClassifier -prop ner.model.props
The training process can be customized using a properties file. Here is an example properties file for training an English model(ner.model.props):
# location of training data
trainFileList = /path/to/conll.3class.train
# location of test data
testFile = /path/to/all.3class.test
# where to store the saved model
serializeTo = ner.model.ser.gz
type = crf
wordFunction = edu.stanford.nlp.process.AmericanizeFunction
useDistSim = false
# establish the data file format
map = word=0,answer=1
saveFeatureIndexToDisk = true
useQN = true
QNsize = 25
# makes it go faster
There is more info about training a CRF model here.
You can learn more about what the various properties above mean here.
SUTime rules can be changed by modifying its included
TokensRegex rule files. Changing other rule-based components (money,
etc.) requires changes to the Java source code.
For more details on the CRF tagger see this page.