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Annotations

Annotations are named values associated with schema items and are designed to hold arbitrary schema-level metadata represented as a str.

There is a number of annotations defined in the standard library. The following are the annotations which can be set on any schema item:

  • title

  • description

  • deprecated

For example, consider the following declaration:

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type Status {
    annotation title := 'Activity status';
    annotation description := 'All possible user activities';

    required property name -> str {
        constraint exclusive
    }
}

The deprecated annotation is used to mark deprecated items (e.g. str_rpad()) and to provide some information such as what should be used instead.

To declare a custom constraint type beyond the three built-ins, add an abstract annotation type to your schema. A custom annotation could be used to attach arbitrary JSON-encoded data to your schema—potentially useful for introspection and code generation.

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abstract annotation admin_note;

type Status {
  annotation admin_note := 'system-critical';
}
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