Symbol eta

The passage around this formula

…possible states before an observation, a is the action just taken, o is the observation that followed, T is the environment’s transition model and O its observation model, the updated belief is $b'(s') = \eta \, O(o \mid s', a) \sum_{s} T(s' \mid s, a)\, b(s)$. with $\eta$ a normalizing constant. Kaelbling, Littman and Cassandra’s original treatment of this update is also where the difficulty is made explicit: they show that the amount of memory an optimal policy needs is not bounded in advance by the size of the problem, and that reducing the reliability of a…

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