linkML support for requiring slot_usage for a slot on its definition

[kheal]

Usecase:
I have a slot, let's call it has_input, that's used across many classes and subclasses. I would love a mechanism in the schema to be able to declare that thehas_input slot must have an associated slot_usage naming its structured_pattern on each class it's used on (including when it's inherited from a parent class).

Ideally, I'd love a way to add this to the definition of the slot along the lines of this:

slots:
  has_input:
    must_be_set_on_induced_slots:
      - structured_pattern

The cherry on top would be the ability to use for subslots as well.
For example:

slots:
  has_connected_class:
    must_be_set_on_induced_slots:
      - structured_pattern

  has_input:
    is_a: has_connected_class

  has_output:
    is_a: has_connected_class

[cmungall]

LinkML does have a mechanism to declare metaschemas and metaclasses, which gets some of the way towards where you want to go, but I don't think it's exactly right for this use case.

Can you say more about expected cases where this would be expected to validate or be invalid?

For example, if has_input is a slot for PlannedProcess, then every proper is_a descendant of PlannedProcess would also need to have a slot usage asserted? Or would it be sufficient for this to be inherited?

[kheal]

I think the slot_usage should be inherited from a parent class (as it currently works, if I understand correctly).

Expected uses for the 2nd example above:

---

VALID:
ClassA with no parent class using has_input slot with a structured_pattern constraint explicitly stated on the class.

INVALID:
ClassA with no parent class using has_input slot without a structured_pattern constraint explicitly stated on the class.

---

Inheritance from abstract class
VALID:
ClassA is abstract. ClassB is_a ClassA. ClassB using slot has_input (either directly or inherited). has_input slot with a structured_pattern constraint stated on the ClassA.

ClassA is abstract. ClassB is_a ClassA. ClassB using slot has_input (either directly or inherited). has_input slot with a structured_pattern constraint stated on the ClassB (but not on ClassA).
this scenario is valid bc ClassA will never be instantiated directly bc its abstract

INVALID:
ClassA is abstract. ClassB is_a ClassA. ClassB using slot has_input (either directly or inherited). has_input slot without a structured_pattern constraint stated on the ClassB nor ClassA

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Essentially the assertion has to be somewhere on the class, whether inherited or asserted directly on the class.