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Yes, that's correct. Ory Keto inherently supports many-to-many relationships, but you can implement many-to-one or one-to-one relationships at the application level. In a many-to-one relationship, many

User

objects could have a relationship to one

Organisation

object. This is naturally supported in Keto as you can add the same

Organisation

relation to many

User

objects. However, if you want to ensure that an

Organisation

can only have a relationship with one

User

(i.e., one-to-many from the

Organisation's

perspective), you would need to enforce this at the application level. This means that when you add a new

User

relation to an

Organisation

, you would first check if a

User

relation already exists for that

Organisation

. If it does, you could choose to not add the new relation, or remove the existing relation before adding the new one. Here are the relevant knowledge sources: - [Define relationships in the OPL](https://www.ory.sh/docs/keto/modeling/create-permission-model#define-relationships-in-the-opl) - [Relation declaration](https://www.ory.sh/docs/keto/reference/ory-permission-language#relation-declaration)