  We consider the theory of stopping bounded processes within the framework of
Hudson--Parthasarathy quantum stochastic calculus, for both identity and vacuum
adaptedness. This provides significant new insight into Coquio's method of
stopping (J. Funct. Anal. 238:149-180, 2006). Vacuum adaptedness is required to
express certain quantum stochastic representations, and many results, including
the proof of the optional-sampling theorem, take a more natural form.
