  When doing inference in ProbLog, a probabilistic extension of Prolog, we
extend SLD resolution with some additional bookkeeping. This additional
information is used to compute the probabilistic results for a probabilistic
query. In Prolog's SLD, goals are nested very naturally. In ProbLog's SLD,
nesting probabilistic queries interferes with the probabilistic bookkeeping. In
order to support nested probabilistic inference we propose the notion of a
parametrised ProbLog engine. Nesting becomes possible by suspending and
resuming instances of ProbLog engines. With our approach we realise several
extensions of ProbLog such as meta-calls, negation, and answers of
probabilistic goals.
