Implementations
Various parsers based on the HPSG formalism have been written and optimizations are currently being investigated. An example of a system analyzing German sentences is provided by the Freie Universität Berlin. In addition the Grammar Group of the Freie Universität Berlin provides open source grammars that were implemented in the TRALE system. Currently there are grammars for German, Mandarin Chinese, Maltese, and Persian that share a common core and are publicly available.
Large HPSG grammars of various languages are being developed in the Deep Linguistic Processing with HPSG Initiative (DELPH-IN). Wide-coverage grammars of German, English and Japanese are available under an open-source license. These grammars can be used with the open-source HPSG systems LKB and PET. DELPH-IN grammars can typically be used for both parsing and generation. Treebanks also distributed by DELPH-IN are being used to develop and test the grammars, as well as train ranking models to decide on plausible interpretations when parsing (or realizations when generating).
Enju is a freely available wide-coverage probabilistic HPSG parser for English developed by the Tsujii Laboratory at The University of Tokyo in Japan. Its robustness sets it apart from most other HPSG parsers.
Read more about this topic: Head-driven Phrase Structure Grammar