In stochastic analysis, a part of the mathematical theory of probability, a predictable process is a stochastic process whose value is knowable at a prior time. The predictable processes form the smallest class that is closed under taking limits of sequences and contains all adapted left-continuous processes.[clarification needed]
Given a filtered probability space ( Ω , F , ( F n ) n ∈ N , P ) {\displaystyle (\Omega ,{\mathcal {F}},({\mathcal {F}}_{n})_{n\in \mathbb {N} },\mathbb {P} )} , then a stochastic process ( X n ) n ∈ N {\displaystyle (X_{n})_{n\in \mathbb {N} }} is predictable if X n + 1 {\displaystyle X_{n+1}} is measurable with respect to the σ-algebra F n {\displaystyle {\mathcal {F}}_{n}} for each n.[1]
Given a filtered probability space ( Ω , F , ( F t ) t ≥ 0 , P ) {\displaystyle (\Omega ,{\mathcal {F}},({\mathcal {F}}_{t})_{t\geq 0},\mathbb {P} )} , then a continuous-time stochastic process ( X t ) t ≥ 0 {\displaystyle (X_{t})_{t\geq 0}} is predictable if X {\displaystyle X} , considered as a mapping from Ω × R + {\displaystyle \Omega \times \mathbb {R} _{+}} , is measurable with respect to the σ-algebra generated by all left-continuous adapted processes.[2] This σ-algebra is also called the predictable σ-algebra.