The intention of this book is to explain to a mathematician having no
previous knowledge in this domain, what "noncommutative probability" is.
So the first decision was not to concentrate on a special topic. For
different people, the starting points of such a domain may be different.
In what concerns this question, different variants are not discussed.
One such variant comes from Quantum Physics. The motivations in this
book are mainly mathematical; more precisely, they correspond to the
desire of developing a probability theory in a new set-up and obtaining
results analogous to the classical ones for the newly defined
mathematical objects. Also different mathematical foundations of this
domain were proposed. This book concentrates on one variant, which may
be described as "von Neumann algebras". This is true also for the last
chapter, if one looks at its ultimate aim. In the references there are
some papers corresponding to other variants; we mention Gudder, S.P. &al
(1978). Segal, I.E. (1965) also discusses "basic ideas".