Annotations

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

Standard annotations

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:

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

5. required property name -> str {
6. constraint exclusive
7. }
8. }

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.

User-defined annotations

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.

1. abstract annotation admin_note;

3. type Status {
4. annotation admin_note := 'system-critical';
5. }

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