 A simple but important example is the effect algebra \([0,1]^{E}\) of functions \(\,f : E \rightarrow [0,1]\), with \(f \perp g\) iff \(f + g \leq 1\) and, in that case, \(f \oplus g = f + g\). One can regard elements of \([0,1]^{E}\) as “unsharp” or “fuzzy” versions of indicator functions \(f : E \rightarrow \{0,1\}\). The set \(\{0,1\}^{E}\) of indicator functions, regarded as a subeffect algebra of \([0,1]^{E}\), is an orthoalgebra and, of course, isomorphic to the boolean algebra of subsets of \(E\).[21]