What does the `schema.yml` file do in a dbt project?

The schema.yml file in a dbt project plays a crucial role in defining metadata for models and documentation. This file is used to organize and describe the various models within the project, including information such as descriptions, column-level documentation, tests, and relationships between models. By providing this structure, it enhances the readability and usability of the data models, making it easier for team members and stakeholders to understand their purpose and usage.

Furthermore, the schema file allows analytics engineers to add tests that validate data integrity and quality, ensuring that the models produce reliable outputs. Documentation generated from the schema.yml can be leveraged to create a clear and comprehensive understanding of the data assets, which is invaluable for knowledge sharing and onboarding processes.

In contrast, the other choices don't accurately represent the function of the schema.yml file. For example, while user access permissions are important in database management, they are not defined in the schema.yml. Similarly, raw data storage and data source specifications are handled through different configurations within dbt and do not belong in the schema file.