BorelSigmaAlgebra - crowlogic/arb4j GitHub Wiki

The Borel σ-algebra(SigmaAlgebra) on a topological space $X$, denoted $\mathcal{B}(X)$, is the smallest σ-algebra containing all the open sets (or equivalently, all the closed sets, compact sets, or continuous real-valued functions). It is generated by the open sets.