# Nelumbo: A new logic meta-language > Source: > Published: 2026-11-11 16:02:53+00:00 Nelumbo is a logic meta-language for specifying declarative languages. You define your DSL's **syntax and semantics** - the semantics in pure logic - and every construct is live on the very next line. Why Nelumbo Language workbenches let you define structure and notation. Nelumbo goes further: you also define what your language *means*, as inference rules - and the language runs while you are still writing it. One pattern line - `Boolean ::= likes ` - and the new notation is first-class syntax, with IDE support included. Meaning is written as inference rules over honest three-valued logic. Logic is the medium, not the target: you write your domain, the engine does the reasoning. Nelumbo executes immediately: a construct defined on line `n` is available from line `n+1` on. No generators, no compile step, no deployment loop. Everything a language workbench gives you, plus executable semantics - with live IDE support in the browser, VS Code, IntelliJ and Eclipse, and an MCP server for AI assistants. See it grow This is real Nelumbo: one line declares new syntax, one rule gives it meaning in logic, and the query at the bottom already speaks the new language - the editor verifies the expected answer live. Try it yourself in the [tutorial](https://nelumbo.nl/tutorial.html); no install needed.