The implemented core grammar for English currently comprises amongst others a traceless analysis of unbounded dependencies and a principled account of English relative clauses without recourse to any empty elements. Babel is a Prolog-implementation of an HPSG fragment of German. A stem lexicon is expanded off-line to yield a full form lexicon which has 3077 entries by now. I use a bottom-up chart parser. The package comes with a number of example grammars, including a Categorial Grammar, a Tree Adjoining Grammar, a Unification Grammar in the spirit of Head-driven Phrase Structure Grammar, an Extraposition Grammar and a Definite Clause Grammar.
Some grammars come with variants of the head-driven generator.
It should not be difficult to adapt an existing NLP system written in Sicstus to Hdrug. It was developed to be a working tool for designing and testing grammars written within the HPSG framework. The system consists of a lexical compiler, constraint processor, chart parser and a module for linking the parser to a graphic interface. Using this system, a user can examine the properties of the HPSG formalism itself, and can investigate characteristics of specific grammars that utilize the formalism. TreeTool is a C program that utilizes the Suntools windowing environment to display graphic trees corresponding to Prolog-style term representations of trees.