  This paper is a study of Glasner's definition of quasi-factors in the setting
of infinite-measure preserving system. The existence of a system with zero
Krengel entropy and a quasi-factor with positive entropy is obtained. On the
other hand, relative zero-entropy for conservative systems implies relative
zero-entropy of any quasi-factor with respect to its natural projection onto
the factor. This extends (and is based upon) results of Glasner, Thouvenot and
Weiss. Following and extending Glasner and Weiss, we also prove that any
conservative measure preserving system with positive entropy in the sense of
Danilenko and Rudolph admits any probability preserving system with positive
entropy as a factor. Some applications and connections with Poisson-suspensions
are presented.
