Let m and l~ be natural numbers with m≥1 and l~≥1, and let T>0 be a real number, called the horizon. For each natural number k≥1 define the record space
Rk(T)={(τ1,…,τk)∈Rk: 0≤τ1≤τ2≤⋯≤τk≤T}⊂Rk,
a subset of Euclidean space.
An observation-driven control policy with horizon T, control dimension m, and l~ channels is a family h=(hk)k≥0 of functions
h0:[0,T]→Rm,hk:[0,T]×Rk(T)×{1,…,l~}k→Rm(k≥1),
such that for every k≥1, every mark vector v∈{1,…,l~}k, and every component index j∈{1,…,m}, the real-valued map (t,τ)↦hkj(t,τ,v) on [0,T]×Rk(T) is measurable with respect to the σ-algebra generated by the relatively open subsets of [0,T]×Rk(T), that is, by the sets U∩([0,T]×Rk(T)) with U an open subset of R1+k; and likewise each component t↦h0j(t) is measurable with respect to the σ-algebra generated by the relatively open subsets of [0,T].