Definition. Feedback operator [ftip-0053]
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    Let \(\mathcal R\) be the set of immutable rollout records and \(\mathcal F\) a typed set of feedback events. A feedback operator is a possibly randomized kernel

    \[\mathsf {Feed}:\mathcal R\rightsquigarrow \mathcal F.\]

    A feedback event may contain an outcome score, step labels, a preference, or an abstention. Its type records which observations were available when it was produced.