http://heartofgold.dfki.de is the current 'official' website where you can find documentation, downloads and papers. There is some additional documentation about installation and troubleshooting at HogInstallation.

The Heart of Gold is a middleware architecture for the integration of deep and shallow natural language processing components. It provides a uniform and flexible infrastructure for building applications that use Robust Minimal Recursion Semantics (RMRS) and/or general XML standoff annotation produced by natural language processing components. The framework uses XSLT as integration language for querying and combining XML standoff markup.

The main purpose Heart of Gold was developed for is integration of various shallow natural language processors with the highly efficient HPSG parser PET in order to increase robustness of HPSG grammars for various languages such as English, German, Japanese, Greek and Norwegian. HPSG grammars can be developed with the LKB, compiled to a binary grammar image, and at runtime executed by PET within the Heart of Gold.

Although the focus of Heart of Gold is deep-shallow integration, the framework itself is generic and hence could also be used to, e.g., combine multiple purely shallow systems on XML basis, or to integrate other deep parsers.

The Heart of Gold has been developed under the wings of the EU-funded project DeepThought and the BMBF-funded project QUETAL and in the context of the DELPH-IN collaboration. The main developer of Heart of Gold is UlrichSchaefer.

The core middleware (and also the PET system) is available under an LGPL open source license. However, some of the components for which we provide adapters are only available for research purposes or have their own licenses different from LGPL.

There is also a mailing list for discussions and announcements concerning Heart of Gold.