Constraint Grammar
Constraint Grammar (CG) is a formalism and methodology in computational linguistics for describing and processing natural language syntax and morphology through declarative rules. It uses constraints to specify permissible or impermissible linguistic structures, enabling tasks like part-of-speech tagging, morphological disambiguation, and shallow parsing. Developed in the 1990s, it is particularly effective for morphologically rich languages and is implemented in tools like the CG-3 compiler.
Developers should learn Constraint Grammar when working on natural language processing (NLP) projects that require robust syntactic analysis, especially for languages with complex inflectional systems like Finnish or Turkish. It is useful for building rule-based systems where high precision and interpretability are prioritized over machine learning approaches, such as in grammar checking, machine translation pre-processing, or linguistic research tools. Its declarative nature makes it easier to maintain and debug compared to purely statistical methods.