---
id: linkml
version: "1.11.1"
license: Apache-2.0
license_treatment: permissive
maintenance: active
---

# linkml — Linked Open Data Modeling Language

License: permissive · Maintenance: active · Downloads: 446.6K/mo

## What it is and what it does

LinkML is a linked data modeling language designed to let you define data schemas once in YAML and generate multiple schema representations—JSON Schema, RDF, ShEx, and others—from that single source. It follows object-oriented and ontological principles, making it useful for domains like healthcare and bioinformatics where semantic interoperability matters. The package includes command-line tools and a Python API for schema generation, validation, and conversion.

You author schemas in YAML, then use LinkML's generators to produce the formats your downstream systems need. It depends on a substantial set of libraries—including jsonschema, rdflib, pydantic, and sqlalchemy—to handle schema validation, RDF processing, and data serialization. The project is actively maintained and supports modern Python versions.

Use it for:

- Define a biomedical data model once in YAML and generate JSON Schema for API validation and RDF for semantic web publishing.
- Convert an existing ontology or schema into multiple formats for use across different tools and platforms.
- Build a domain-specific schema language for internal data governance, then auto-generate documentation and validation code.
- Create linked data models that integrate with existing RDF and OWL ecosystems.
- Generate TypeScript or Python classes from a YAML schema definition for type-safe data handling.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

LinkML is a modeling language for defining linked data schemas in YAML, with tools to generate JSON, RDF, and other schema formats from a single source definition.

Yes, if you need to author schemas once and generate multiple formats (JSON Schema, RDF, ShEx) from a single source. The active maintenance, permissive license, low install friction, and support for current Python versions make it a solid choice. No known vulnerabilities. Best suited for teams working with linked data, semantic web standards, or multi-format schema requirements.

## Install

pip install linkml
uv add linkml
poetry add linkml

## Installing linkml

Before you install: Low install friction with a pure-Python wheel. Active maintenance with a release within the last 86 days. Supports current Python versions (3.10–3.13).

License in practice: Apache-2.0 permissive license allows commercial and private use with minimal restrictions.

Quickstart:

pip install linkml

from linkml.loaders import yaml_loader
from linkml.generators.jsonschemagen import JsonSchemaGenerator

schema = yaml_loader.load('my_schema.yaml')
generator = JsonSchemaGenerator(schema)
json_schema = generator.serialize()

Requires Python 3.10 or later.

Verify before relying:

- Specific documentation on schema validation and error handling during conversion.
- Performance characteristics when working with large or deeply nested schemas.
- Community adoption metrics beyond download counts (e.g., active issue resolution, contributor base).

## Package facts

- License: Apache-2.0 (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 446.6K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

linked data schema modeling, yaml to json schema conversion, rdf schema generation, ontology definition language, data model to multiple formats, semantic web schema tools, biolink compatible modeling, schema-generation, linked-data, semantic-web

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