Retire prediction market UIA after defining event occurs

Perhaps two sections for prediction market UIAs, 'Active' or 'Open' for user-issued assets that are defined by events yet to occur, and 'Retired' or 'Concluded' or 'Closed' for those defined by events in the past.

A quick skim of tokens makes me think that a structured creation form would be good, too, to make sure that event details are fully specified, and operational definitions of how event outcome will be determined are fully specified (the more automatic this is, the better).

Start with the issue text and the repository's BitShares Improvement Proposal process. Clarify whether the work is to define lifecycle sections for prediction market UIAs, specify a structured creation form, or formalize event-outcome rules. Done means the proposal has an agreed scope and complete operational definitions; no implementation files or tests are named.

Written by the indexing model from the issue text.