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Section: Software

ACG Development Toolkit

In order to support the theoretical work on ACG, we have been developing a support system. The objectives of such a system are twofold:

  1. to make possible to implement and experiment grammars the modeling of linguistic phenomena;

  2. to make possible to implement and experiment results related to the ACG formalisms. Such results can concern parsing algorithms, type extensions, language extensions, etc.

The current version of the the ACG development toolkit prototype(Available at http://acg.gforge.inria.fr with a CeCILL license.) issues from a first release published in October 2008. Further releases have been published before the ESSLLI 2009 course on ACG. It focuses on providing facilities to develop grammars. To this end, the type system currently implemented is the linear core system plus the (non-linear) intuitionistic implication, and a special attention has been paid to type error management. As a major limitation, this version only considers transformation from abstract terms to object terms, and not the other way around.

Enabling transformation from the object terms to the abstract terms is the first step of future development for the ACG support system. A parsing algorithm based on  [37] 's methods is being implemented for second-order ACGs. It is based on a translation of ACG grammars into Datalog programs and is well-suited to fine-grained optimization. A summer internship from ENS Cachan, Clovis Eberhart (L3) has been implementing the translation from the higher-order signatures and terms data structures to the Datalog clauses data structures. It still remains to be integrated to the main branch.

In order to allow for a larger character set as input, another extension implemented this summer by another internship from École des Mines de Nancy, Grégoire Brenon (M1) was to extend the lexer and the parser for the data files with UTF-8 capabilities (OCaml lacks such a built-in capability).

However, since we're interested not only by recognizability (hence whether some fact is provable) but also by the parsing structure (hence the proof), the Datalog solver requires further adaptations. Note however that in the general case, the decidability of translating an object term to an abstract one is still an open problem.