Cyc Core API Specification

Latest release: Maven Central
License: Apache 2.0
Changes: See the CHANGELOG
Documentation: Cyc Developer Center

The Cyc Core API is the core set of Java APIs for interacting with the Cyc inference engine and knowledge base. It consists of three interrelated APIs:

The reference implementation of the Core API may be found in the api-clients repository, in the core-client directory. For further details about the Core Client, see the project’s README.



  • Java 8 or greater to run, JDK 1.8 or greater to build.
  • Apache Maven version 3.2 or higher to build the sources. If you are new to Maven, you may wish to view the quick start.

The APIs may be used without Maven via the cyc-core-api-1.1.1-jar-with-dependencies.jar. See Standalone Bundle, below.

Cyc Server

The following Cyc server releases are supported:

  • ResearchCyc 4.0q or higher. Requires server code patching (see below).
  • EnterpriseCyc 1.7-preview or higher. Requires server code patching.

For inquiries about obtaining a suitable version of Cyc, please visit the Cyc Dev Center downloads page.

Server Code Patching

As of version 1.0.0-rc3, the Core Client implementation requires SubL code patches which are not present in ResearchCyc 4.0q or EnterpriseCyc 1.7-preview. These patches can be applied manually, or they can be automatically applied by the API bundle itself. For details, see in the core-client project.


Apache Maven

To use the Cyc Core APIs in a Maven project, add the following dependency to your pom.xml:


You’ll normally want to also include the Core Client reference implementation:


The Core APIs use the SLF4J logging API. They do not include a logging implementation, but instead allow you to specify your own. For example, to use Log4J 1.2:


For more details about logging, see the Cyc API logging HOWTO.

Standalone Bundle

If you’re not using Apache Maven, or can’t allow Maven to retrieve dependencies from the Internet, you may download a core-client standalone bundle containing:

  • A standalone jar-with-dependencies for the Core API specification.
  • A standalone jar-with-dependencies for the Core Client implementation.
  • A test suite. (Requires Maven to compile.)
  • Source code. (Requires Maven to compile.)
  • Example code. (Requires Maven to compile.)

The bundle is available from the releases page as a tar or zip file. See the README in the bundle for details.

Building the Sources

Within the core-api project, issue the following command:

mvn install

There are currently no tests included.

Of course, you will need an implementation in order to use the Core APIs. You may wish to build the core-client project; see that project’s README for details.

Further Documentation

For the latest API documentation and news, or to ask questions, visit the Cyc Developer Center.

Code samples may be downloaded from the Cyc Core API Use Cases project in the example-code repository.


Issues may be reported via the Cycorp issue tracker.

For questions about the APIs or general issues with using them, please visit the Cyc Dev Center.