id
The unique URI of the schema. When applicable, service providers
MUST specify the URI, e.g.,
"urn:ietf:params:scim:schemas:core:2.0:User". Unlike most other
schemas, which use some sort of Globally Unique Identifier (GUID)
for the "id", the schema "id" is a URI so that it can be
registered and is portable between different service providers and
clients. REQUIRED.
There should be a validator that checks that ids are URNs.
RFC7643 §7 indicates:
There should be a validator that checks that ids are URNs.