SpiceDB is an open source, Google Zanzibar-inspired, database system for creating and managing security-critical application permissions.

SpiceDB

Hey all - quick question about SpiceDB schemas. Given this folder schema:
```zed
definition user {}
definition folder {
   relation parent: folder
   relation member: user
   permission view = member + parent->member
}
```
A folder's `parent` relation could technically have multiple folders written to it. Is there a way to enforce single-parent (no multiple ancestors) at the schema level, or does that constraint have to live in application logic?

right now it has to live in application logic

we're bouncing around a proposal internally that would let you specify that invariant in the schema and then have it be enforced by SpiceDB, but it's not currently on the roadmap