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The OpenCalais Enhancement Engine

The OpenCalais Enhancement Engine provides an interface to the OpenCalais Webservice for Named Entity Recognition (NER).

Technical description

The engine will send the text of content item to the OpenCalais service and retrieve the NER annotations in RDF format. The OpenCalais annotations are added to the content item's metadata as specified by the Stanbol Enhancement Structures.

The engine natively supports the mime types text/plain and text/html. Additionally, text can be processed that is provided in the content item's metadata as value of the property

http://www.semanticdesktop.org/ontologies/2007/01/19/nie#plainTextContent

Supported languages are

• English (en)
• French (fr)
• Spanish (es)

Requirements for use and configuration options

The use of this component requires an API key from OpenCalais. Without providing an API key, the engine will not do anything. Such a key can be obtained from http://www.opencalais.com/APIkey.

In the OSGi configuration the key is set as value of the property

org.apache.stanbol.enhancer.engines.opencalais.license

Also, the unit tests require the API key. Without the key some tests will be skipped. For Maven the key can be set as a system property on the command line:

mvn -Dorg.apache.stanbol.enhancer.engines.opencalais.license=YOUR_API_KEY [install|test]

The following configuration properties are defined:

• org.apache.stanbol.enhancer.engines.opencalais.license: The OpenCalais license key that must be defined.
• org.apache.stanbol.enhancer.engines.opencalais.url: The URL of the OpenCalais RESTful service. That needs only be changed when OpenCalais should change its web service address.

• org.apache.stanbol.enhancer.engines.opencalais.typeMap: The value is the name of a file for mapping the NER types from OpenCalais to other types. By default, a mapping to the DBPedia types is provided in order to achieve compatibility with the Stanbol OpenLNLP-NER engine. If no mapping is desired one might pass an empty mapping file. Types for which no mapping is defined are passed as is to the metadata. The syntax of the mapping table is similar to that of Java property files. Each entry takes the form

  :::text CalaisTypeURI=TargetTypeURI

• org.apache.stanbol.enhancer.engines.opencalais.NERonly: A Boolean property to specify whether in addition to the NER enhancements also the OpenCalais Linked Data references are included as entity references. By default, these are omitted.

Usage

Assuming that the Stanbol endpoint with the full launcher is running at

http://localhost:8080

the license key has been defined and the engine is activated, from the command line commands like this can be used for submitting some text file as content item:

• stateless interface

  :::bash curl -i -X POST -H "Content-Type:text/plain" -T testfile.txt http://localhost:8080/engines

• stateful interface

  :::bash curl -i -X PUT -H "Content-Type:text/plain" -T testfile.txt http://localhost:8080/contenthub/content/someFileId

Alternatively, the Stanbol web interface can be used for submitting documents and viewing the metadata at

http://localhost:8080/contenthub