In this NIP (Nostrum Improvement Proposal), we see a new way of handling events in the Nostrum network. This proposal defines how events can be delegated so that they can be signed by other keypairs. It also abstracts away the use of the 'root' keypairs when interacting with clients, allowing users to generate new keypairs for each client and authorize those keypairs to generate events on behalf of their root pubkey. The query string supports conditions based on event kind and timestamp, which can be combined using the `&` operator.

Link: https://github.com/nostr-protocol/nips/blob/master/26.md