Tonto is a textual DSL for creating OntoUML models grounded in the Unified Foundational Ontology (UFO). It gives ontology projects a source-controlled, code-like format while keeping the modeling concepts explicit enough for validation, transformation, visualization, and reuse.

The repository is an npm workspace that contains the Tonto language and CLI, the VS Code extension, the package manager, the documentation site, and the diagram/webview integration used by the extension.

• Textual syntax for OntoUML/UFO constructs such as kinds, roles, phases, relators, datatypes, enumerations, relations, and generalization sets.
• A Langium-based language server for validation, completion, hover information, semantic highlighting, formatting, references, and editor integrations.
• CLI commands for project initialization, JSON generation/import, local validation, gUFO transformation, and PlantUML diagram generation.
• A VS Code extension with .tonto editing, command views, diagram previews, PlantUML previews, and optional .tontodiagram editing.
• TPM, the Tonto Package Manager, for installing Git-based ontology dependencies declared in tonto.json.
• A self-hosted documentation site built from the repository content.

flowchart LR
    User["Tonto modeler"] --> Extension["packages/extension<br/>VS Code extension"]
    User --> CLI["packages/tonto<br/>tonto-cli"]
    Extension --> Language["Langium language server<br/>from tonto-cli"]
    Extension --> Webview["packages/webview<br/>diagram UI bundle"]
    Webview --> SprottyWebview["packages/sprotty-vscode-webview"]
    Extension --> SprottyHost["packages/sprotty-vscode"]
    CLI --> OntoUML["OntoUML JSON"]
    CLI --> GUFO["gUFO / Turtle"]
    CLI --> PlantUML["PlantUML diagrams"]
    CLI --> TPM["packages/tpm<br/>dependency install"]
    TPM --> Dependencies["tonto_dependencies/"]
    Docs["packages/tonto-documentation<br/>Next.js docs"] --> User

• Node.js and npm. Use Node 24 or newer when developing the whole workspace because the documentation package declares node >=24.0.0.
• npm 7.7.0 or newer for workspace support.
• VS Code when developing or testing the extension.
• Git when using TPM dependency installation.

Some publishable packages declare lower runtime minimums, but Node 24 keeps the full monorepo build and documentation workflow aligned.

From the repository root:

npm install

npm run build
npm run watch
npm run lint
npm run test
npm run docs:dev
npm run docs:check

Useful package-scoped commands:

npm run langium:generate
npm run build --workspace=tonto-cli
npm run build --workspace=tonto
npm run build --workspace=tonto-sprotty-webview
npm run build --workspace=tonto-documentation

1. Install dependencies from the repository root.
2. Run the default VS Code build task with Cmd+Shift+B, or run npm run watch.
3. Open the debug panel and launch Run Extension.
4. In the Extension Development Host, open or create a .tonto file.

The extension starts the language server from the extension bundle and registers commands for JSON generation, JSON import, validation, gUFO transformation, TPM install, project initialization, guidance generation, semantic token color setup, and diagram previews.

After building or installing tonto-cli, create or inspect a project with:

tonto-cli init
tonto-cli generate .
tonto-cli validate .
tonto-cli validate . --with-api
tonto-cli transform .
tonto-cli plantuml . --per-package

See packages/tonto/README.md for the complete command table and syntax overview.

A typical Tonto project contains:

my-ontology/
|-- src/
|   `-- main.tonto
|-- tonto.json
|-- tonto_dependencies/
`-- generated/

Minimal .tonto example:

package university

kind Person {
    name: string
}

role Student specializes Person
kind Course {
    code: string
}

@material relation Student [0..*] -- enrollsIn -- [0..*] Course

The documentation site lives in packages/tonto-documentation.

npm run docs:dev
npm run docs:check

The GitHub Pages workflow builds the static site from the documentation workspace.

Package the VS Code extension from packages/extension:

npm run package --workspace=tonto

Publish commands exist in individual package workspaces and require the appropriate npm or VS Code Marketplace credentials:

npm run publish --workspace=tonto-cli
npm run publish --workspace=tonto

Distributed under the MIT License. See LICENSE for more information.

Matheus Lenke Coutinho - matheus.l.coutinho@edu.ufes.br - LinkedIn - GitHub