Do memberships have enabled/disabled dates?
Can you filter by immediate, nonimmediate, all memberships (i.e. immediate if it can be directly unassigned, non immediate if due to another membership)?

Do memberships have enabled/disabled dates? Yes, I think this is useful in the underlying groups store, though not sure if it needs to be supported in the fifer API
Can you filter by immediate, nonimmediate, all memberships (i.e. immediate if it can be directly unassigned, non immediate if due to another membership)? If this is used by UI, then you need to know if something can be directly unassigned, i.e. an immediate vs non-immediate

KIM has requirements to track this, but could be tracked as part of the service implementation at least initially. Ultimately though there may be a need to access historical group information via the api, but it may not be needed up front. The KIM UI though does allow for specifying group members and giving them a start and end date, so to fully build our UIs on top of such an api that would need to be available.
I think this is equivalent to the concept of "direct" group membership in KIM. If so, the answer would be "yes".

No.
Yes. The current uPortal groups API offers methods for both children and parent lookups that distinguish between immediate and inherited relationships.

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