Understanding "but not" operator on a relation

[Raid55]

In the DSL Model below:

type user

type workspace
  relation member: [user]
  relation guest: [user]

type document
  relations
    define workspace: [workspace]
    define owner: [user] but not guest from workspace # <-- this line specifically
    define full_access: [user, workspace#member] or owner
    define edit: [user, workspace#member] or full_access
    define view: [user, user:*, workspace#member] or edit

Does the owner relation on the document type ensure that a guest of the parent workspace can't be written (using .write) as an owner of a document or does this just ensure that in case that tuple exists a .check call will deny access?

[rhamzeh]

Hi @Raid55

It affects the Check - so if tuples are written to indicate someone is both an owner and a guest, the check for owner will return false.

If you want to have a check on write, you should treat it as any other action:

• add a relation called can_be_written_as_owner
• before calling the Write, call Check to ensure that the action of writing can proceed