Restrictions

To provide flexibility and extensibility, DTDL does not have a way of restricting attributes to specific values or object types. But you can define information to clarify what the intention of an attribute is and what values should be expected.

For values of the 'object' type, you can specify a set of classes you expect the objects to have when linked by this value. The system does not guarantee that the object has all of those classes or restricts operations that cause a violation of these rules.

// attribute 'val_obj' of type q in namespace a::b should contain class 'type_t'
objecttype a::b::q.val_obj(type_t);