fully formalized HPSG grammars

[Tobias Sing]

In another thread, Carl Pollard wrote:

> Fully formalized HPSG grammars are written in a formal language (such
> as RSRL) with a model-theoretic interpretation and a proof
> theory.

Are there any papers or book chapters you could recommend that treat the
formalization of HPSG or feature-based grammars in general?

Best regards,
Tobias

--
Tobias Sing
Department of Computer Science
University of Freiburg
http://www.informatik.uni-freiburg.de/~sing