Various known models of probabilistic XML can be represented as instantiations of abstract p-documents. Such documents have, in addition to ordinary nodes, distributional nodes that specify the probabilistic process of generating a random document. Within this abstraction, families of pdocuments, which are natural extensions and combinations of previous models, are considered. The focus is on efficiency of applying twig queries (with projection) to p-documents. A closely related issue is the ability to (efficiently) translate a given document of one family into another family. Furthermore, both of these tasks have two variants that correspond to the value-based and object-based semantics.