A constraint-based bottom-up counterpart to Definite Clause Grammars

A new grammar formalism, CHR Grammars (CHRG), is proposed that provides a constraint-solving approach to language analysis, built on top of the programming language of Constraint Handling Rules in the same way as Definite Clause Grammars (DCG) on Prolog. CHRG works bottom-up and adds the following features when compared with DCG: (i) An inherent treatment of ambiguity without backtracking. (ii) Robust parsing; do not give up in case of errors but return the recognized phrases. (iii) A flexibility to produce and consume arbitrary hypotheses making it straightforward to deal with abduction, integrity constraints, operators 6 la assumption grammars, and to incorporate other constraint solvers. (iv) Context-sensitive rules that apply for disambiguation, coordination in natural language and tagger-like rules.