Table of contents


The Open Information Extraction (OpenIE) annotator extracts open-domain relation triples, representing a subject, a relation, and the object of the relation. For example, born-in(Barack Obama, Hawaii). This is useful for (1) relation extraction tasks where there is limited or no training data, and it is easy to extract the information required from such open domain triples; and, (2) when speed is essential. The system can process around 100 sentences per second per CPU core. The Collection of extracted relation triples are stored under the RelationTriplesAnnotation key of a CoreMap (i.e., sentence). The OpenIE annotator (openie) requires the natural logic annotation (natlog).

In addition to extracting relation triples, the annotator produces a number of sentence fragments corresponding to entailed fragments from the given original sentence. These are stored on the EntailedSentencesAnnotation key of a CoreMap (i.e., sentence).

Property nameAnnotator class nameGenerated Annotation
openieOpenIEEntailedSentencesAnnotation, RelationTriplesAnnotation


All option are specified as Properties. The value of a property is always a String. The type referred to here is how the String will be interpreted/parsed.

The final group of options for specifying models are provided to fine-tune the inner workings of the OpenIE system. These should be changed only in very rare situations; for example, if you are developing extensions to the system itself.

Option nameTypeDefaultDescription
openie.formatEnumdefaultOne of {reverb, ollie, default, qa_srl}. Changes the output format of the program. Default will produce tab-separated columns for confidence, the subject, relation, and the object of a relation. ReVerb will output a TSV in the ReVerb format. Ollie will output relations in the default format returned by Ollie.
openie.filelistfilepathnullA path to a file, which contains files to annotate. Each file should be on its own line. If this option is set, only these files are annotated and the files passed via bare arguments are ignored.
openie.threadsintegernumber of coresThe number of threads to run on. By default, this is the number of cores in the system.
openie.max_entailments_per_clauseinteger1000The maximum number of entailments to produce for each clause extracted in the sentence. The larger this value is, the slower the system will run, but the more relations it can potentially extract. Setting this below 100 is not recommended; setting it above 1000 is likewise not recommended.
openie.resolve_corefbooleanfalseIf true, run coreference (and consequently NER as a dependency of coreference) and replace pronominal mentions with their canonical mention in the text.
openie.ignore_affinitybooleanfalseWhether to ignore the affinity model for prepositional attachments.
openie.affinity_probability_capdouble1/3The affinity value above which confidence of the extraction is taken as 1.0.
openie.triple.strictbooleantrueIf true, extract triples only if they consume the entire fragment. This is useful for ensuring that only logically warranted triples are extracted, but puts more burden on the entailment system to find minimal phrases (see -max_entailments_per_clause).
openie.triple.all_nominalsbooleanfalseIf true, extract nominal relations always and not only when a named entity tag warrants it. This greatly overproduces such triples, but can be useful in certain situations.
openie.splitter.modelfilepath You can override the default location of the clause splitting model with this option.
openie.splitter.nomodelbooleanfalseRun without a clause splitting model – that is, split on every clause.
openie.splitter.disablebooleanfalseDon’t split clauses at all, and only extract relations centered around the root verb.
openie.affinity_modelsfilepath A custom directory or classpath folder location to read the affinity models for PP/obj attachments from.


The OpenIE system can be run both through the command line, and through the CoreNLP API

Command Line

An interactive command-line shell can be run with the command:

java -mx1g -cp stanford-corenlp-<version>.jar:stanford-corenlp-<version>-models.jar:CoreNLP-to-HTML.xsl:slf4j-api.jar:slf4j-simple.jar edu.stanford.nlp.naturalli.OpenIE

In addition, the program can be run on a collection of files either by passing the files directly as command-line arguments:

java -mx1g -cp stanford-corenlp-<version>.jar:stanford-corenlp-<version>-models.jar:CoreNLP-to-HTML.xsl:slf4j-api.jar:slf4j-simple.jar edu.stanford.nlp.naturalli.OpenIE  /path/to/file1  /path/to/file2 

or by setting the -filelist argument to a file containing a list of files to annotate, one per line:

java -mx1g -cp stanford-corenlp-<version>.jar:stanford-corenlp-<version>-models.jar:CoreNLP-to-HTML.xsl:slf4j-api.jar:slf4j-simple.jar edu.stanford.nlp.naturalli.OpenIE  -filelist /path/to/filelist


Relation triples can be accessed through the CoreNLP API using the standard annotation pipeline. An example class which does this is given below:

import edu.stanford.nlp.ling.CoreAnnotations;
import edu.stanford.nlp.pipeline.Annotation;
import edu.stanford.nlp.pipeline.StanfordCoreNLP;
import edu.stanford.nlp.naturalli.NaturalLogicAnnotations;
import edu.stanford.nlp.util.CoreMap;

import java.util.Collection;
import java.util.Properties;

/** A demo illustrating how to call the OpenIE system programmatically.
public class OpenIEDemo {

  public static void main(String[] args) throws Exception {
    // Create the Stanford CoreNLP pipeline
    Properties props = new Properties();
    props.setProperty("annotators", "tokenize,pos,lemma,depparse,natlog,openie");
    StanfordCoreNLP pipeline = new StanfordCoreNLP(props);

    // Annotate an example document.
    Annotation doc = new Annotation("Obama was born in Hawaii. He is our president.");

    // Loop over sentences in the document
    for (CoreMap sentence : doc.get(CoreAnnotations.SentencesAnnotation.class)) {
      // Get the OpenIE triples for the sentence
      Collection<RelationTriple> triples =
      // Print the triples
      for (RelationTriple triple : triples) {
        System.out.println(triple.confidence + "\t" +
            triple.subjectLemmaGloss() + "\t" +
            triple.relationLemmaGloss() + "\t" +

Simple CoreNLP API

The Simple CoreNLP API includes bindings for the OpenIE system, via the method Sentence.openieTriples(). An example usage is given below:

import edu.stanford.nlp.simple.*;

/** A demo illustrating how to call the OpenIE system programmatically.
public class OpenIEDemo {

  public static void main(String[] args) throws Exception {
    // Create a CoreNLP document
    Document doc = new Document("Obama was born in Hawaii. He is our president.");

    // Iterate over the sentences in the document
    for (Sentence sent : doc.sentences()) {
      // Iterate over the triples in the sentence
      for (RelationTriple triple : sent.openieTriples()) {
        // Print the triple
        System.out.println(triple.confidence + "\t" +
            triple.subjectLemmaGloss() + "\t" +
            triple.relationLemmaGloss() + "\t" +

More Information

More information can be found on the Open IE homepage.