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Just as object-oriented languages let you extend a class to inherit its properties, you can extend an existing Standard to create a new Standard that inherits all of the parent’s constraints. This lets you build on shared definitions without duplicating constraint declarations, keeping your schema DRY and consistent across related record types.

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Extension Syntax

To extend a Standard, declare your new Standard name and reference as usual, then append a colon followed by the parent Standard’s reference prepended with @:
The new Standard inherits every constraint defined in the parent Standard. Your existing queries and references to the parent Standard are unaffected — extension creates a completely separate table.

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Basic Example

A common use case is modeling different vehicle types. You can extend the base vehicle Standard to create a truck Standard that inherits all vehicle constraints:
With this single line, TRCK has all of the same constraints as VHL — vin, make, model, and any others defined in vehicle — stored in its own dedicated table.

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Adding Extra Constraints

You can give your extended Standard additional constraints by including a constraint block. The extended Standard will contain all parent constraints plus any new ones you define:
In this example, TRCK inherits all constraints from VHL and adds two more:
  • owner — a reference to a PER (person) Standard record, required on every truck.
  • max_weight — a double value representing the truck’s maximum weight, optional.
Use extension when two record types share a common structure but need to be queried and stored independently. Avoid extending a Standard just to add a single boolean flag — in that case, adding the constraint directly to the parent Standard may be cleaner.
Extension is not inheritance in the runtime sense — it copies the constraint structure at definition time. Changes to the parent Standard’s constraints after extension are not automatically reflected in the extended Standard.