M3L — Meta Model Markup Language

Markdown-based data modeling language. Write data models in readable Markdown, parse them into machine-processable AST.

## User
- name: string(100) @not_null
- email: string(320)? @unique
  > Primary contact email.
  > Used for login and account recovery.
- role: enum = "user"
  - admin: "Administrator"
  - user: "Regular User"
- created_at: timestamp = `now()`

# Lookup
- department_name: string @lookup(department_id.name)

# Computed
- display_name: string @computed(`name + ' <' + email + '>'`)

Design Principles

M3L is a Markdown extension — not a separate language that borrows Markdown syntax, but Markdown itself with semantic meaning layered on top.

1. Readable and writable — a .m3l.md file should be comfortable to read and write as plain Markdown. No special editor required.
2. Valid Markdown — every M3L file renders as meaningful documentation in any Markdown viewer (GitHub, VS Code, Obsidian, etc.). Syntax choices must never break the viewing experience.
3. Markdown semantics preserved — heading levels (#, ##, ###), lists (-), blockquotes (>), and code fences retain their Markdown meaning. M3L adds schema semantics on top, not instead.
4. Minimal surprise — if a construct looks like standard Markdown, it should behave like standard Markdown. Parser behavior must align with what a Markdown-literate user would expect.
5. Parser is a consumer, not an owner — the parser interprets the document; it does not define what Markdown means. Unrecognized Markdown constructs should be tolerated, not corrupted.

What This Repo Provides

This repository is the specification and parser for M3L. It provides:

1. Language Specification — the formal definition of M3L syntax, types, and semantics
2. Rust Core Parser — single canonical implementation (m3l-core)
3. CLI Tool — m3l parse, m3l validate, m3l lint, m3l format, m3l diff, m3l analyze
4. Lint Framework — configurable style & quality rules (m3l-lint)
5. Language Bindings — Node.js (NAPI), C# (P/Invoke), WASM

What this repo does NOT do: code generation, database migration, UI scaffolding, or any other output. Those are the responsibility of consumer applications that depend on the M3L parser to read the AST.

.m3l.md files ──> [ M3L Parser ] ──> AST (JSON) ──> [ Your App ]
                   ^^^^^^^^^^^^^^                     ^^^^^^^^^^^^
                   this repo                          your repo

Features

• Markdown-native — valid Markdown, renders in any viewer
• Models, enums, interfaces, views — full data modeling support
• Inheritance — ## Child : Parent with field resolution
• Lookup / Rollup / Computed fields — derived field definitions
• Backtick expressions — @computed(`expr`), = `now()` for unambiguous expressions
• Multi-line computed — fenced code blocks for complex expressions (CASE, multi-line SQL)
• Derived views — with source, where, order_by, joins, or raw SQL code blocks
• Field blockquote descriptions — > multi-line docs attached to fields
• Attribute Registry — define custom @ attributes with ::attribute type indicator
• 3-tier attribute classification — standard, registered, unregistered
• Custom framework attributes — `[FrameworkAttr]` with structured parsing
• Validation — 14 semantic diagnostics (M3L-E001E010, W001W004)
• Multi-file — directory scanning with @import and m3l.config.yaml

Bindings

All bindings share the same Rust core parser (m3l-core), ensuring identical behavior.

Binding	Platform	Package
CLI	Any (native binary)	m3l parse, validate, lint, format, diff, analyze
Node.js	NAPI native addon	@iyulab/m3l
C#	P/Invoke (.NET 8.0+)	M3L.Native
WASM	Browser / Node.js	@iyulab/m3l-wasm

Quick Start

CLI

cargo install m3l-cli

m3l parse ./models                  # Output AST as JSON
m3l validate ./models --strict      # Validate with diagnostics
m3l validate ./models --format json # Machine-readable output
m3l lint ./models                   # Style & quality checks
m3l lint ./models --format sarif    # SARIF 2.1.0 output (GitHub Code Scanning)
m3l format ./models                 # Standardize M3L formatting
m3l diff old.m3l.md new.m3l.md      # Compare two schemas
m3l analyze ./models                # Dependency graph (Mermaid)
m3l analyze ./models --format dot   # Dependency graph (DOT/Graphviz)

Node.js

npm install @iyulab/m3l

const { parse, validate } = require('@iyulab/m3l');

const result = JSON.parse(parse('## User\n- name: string', 'user.m3l.md'));
console.log(result.data.models[0].name); // "User"

const diag = JSON.parse(validate('## User\n- name: unknown_type', '{}'));
console.log(diag.data.errors); // [{ code: "M3L-E009", ... }]

C# / .NET

dotnet add package M3L.Native

using M3L.Native;

var json = M3lNative.Parse("## User\n- name: string", "user.m3l.md");
var result = M3lNative.ParseTyped("## User\n- name: string", "user.m3l.md");
Console.WriteLine(result?.Success); // True

Documentation

• M3L Specification — full language spec (syntax, types, grammar)
• Examples — sample M3L files

Project Structure

crates/
  m3l-core/           # Rust core parser (lexer → parser → resolver → validator)
  m3l-cli/            # CLI tool (parse, validate, lint, format, diff, analyze)
  m3l-lint/           # Lint framework (naming, model-size, similar-fields, relation-complexity)
  m3l-cabi/           # C ABI cdylib (for P/Invoke / ctypes)
  m3l-wasm/           # WASM (wasm-bindgen)
  m3l-napi/           # Node.js native addon (napi-rs)
bindings/
  typescript/         # @iyulab/m3l npm package wrapper
  csharp/             # M3L.Native NuGet package (P/Invoke)
spec/
  conformance/        # Shared test fixtures (inputs + expected JSON)
docs/
  specification.md    # M3L language specification
samples/              # Example .m3l.md files

License

MIT