In the framework of models generated by compositional expressions, we solve two topical marginalization problems (namely, the \emph{single-marginal problem} and the \emph{marginal-representation problem}) that were solved only for the special class of the so-called "canonical expressions". We also show that the two problems can be solved "from scratch" with preliminary symbolic computation.
Efficient computational algorithms are what made graphical Markov models so popular and successful. Similar algorithms can also be developed for computation with compositional models, which form an alternative to graphical Markov models. In this paper we present a theoretical basis as well as a scheme of an algorithm enabling computation of marginals for multidimensional distributions represented in the form of compositional models.