Two random processes on the time interval 1 appear, roughly speaking, when conditioning the Wiener process to vanish on both ends of With no further conditioning, the process takes both positive and negative values on [0, 1 and is called Brownian bridge. Conditioned also to stay positive on (0, 1), the process is called Brownian excursion. In both cases a rigorous treatment involves a limiting procedure, since the formula "P"("A"|"B") = "P"("A" ∩ "B")/"P"("B") does not apply when "P"("B") = 0.