Introduction

What is metadata?

Your Hasura metadata describes your supergraph and its subgraphs. This metadata is used to build your supergraph, the connectors that link your data sources to models and commands in your API, and the various relationships and permissions that link together types from data sources and restrict access control using permissions within each subgraph.

This metadata is written in Hasura Metadata Language (HML), which is a declarative extension of YAML. It is used to describe the structure of your supergraph, the data sources that it connects to, and the relationships and permissions that define how your data can be accessed. The metadata is used to generate the GraphQL schema that defines your API.

Tools

Hasura DDN provides a set of tools to help you manage your metadata:

• The Hasura DDN CLI, which will scaffold your metadata and provide a set of commands to help you manage it.
• The Hasura VS Code extension, which provides syntax highlighting, auto-complete, metadata validation, and more.

Next steps

On each page in this section, you'll find detailed information about the various components of Hasura DDN which you can author and modify in your metadata. Each page will provide you with an overview of the components, how they work, and examples of how to use them. Below all of this, you'll find detailed reference information about the metadata structure and the fields that you can use to define each component.