grammar-based generation

**Grammar-based generation** is the **constrained decoding method that permits only token sequences valid under a formal grammar definition** - it enforces structural correctness by design. **What Is Grammar-based generation?** - **Definition**: Output generation guided by context-free or custom grammars. - **Mechanism**: At each step, invalid token continuations are masked according to parser state. - **Target Formats**: JSON, SQL subsets, command languages, and domain-specific syntaxes. - **Runtime Dependency**: Requires grammar parser integration with tokenizer-aware decoding. **Why Grammar-based generation Matters** - **Syntactic Correctness**: Guarantees outputs conform to required grammar rules. - **Automation Safety**: Reduces parser failures and downstream execution errors. - **Policy Control**: Restricts output language to approved constructs. - **Operational Efficiency**: Avoids costly retry loops caused by malformed text. - **Trust**: Users and systems can rely on structurally valid responses. **How It Is Used in Practice** - **Grammar Design**: Write minimal unambiguous grammars matching actual consumer expectations. - **Tokenizer Alignment**: Map grammar terminals to tokenization behavior and escape rules. - **Coverage Testing**: Run fuzz tests on edge-case prompts to verify grammar completeness. Grammar-based generation is **a deterministic path to structurally valid generated output** - well-engineered grammars convert free text generation into reliable formal output.