The ext library includes miscellaneous utility functions, extensions to the OCaml standard library (including List and Array), and two utility modules, Timer and Heap (priority queue implemented as a binary heap).

The Ocaml Expat library provides an interface to the Expat XML Parser.

The lbfgs library acts as a simple wrapper to the C LBFGS library written by Naoaki Okazaki.

The Pll module performs efficient computation of pseudo-likelihood and its gradient, given a Markov network represented as a set of weighted conjunctive features.

The BN library reads, writes, and represents Bayesian networks (BNs) and dependency networks (DNs) with conditional probability distributions (CPDs) that are tree-structured, tables, or arbitrary sets of factors.

The Circuit module provides an interface for working with arithmetic circuits, so that learning and inference algorithms can be built on top of this data structure/inference representation.

The Data module reads/writes data and schema files, which have a common format throughout Libra

SPN library provides data structure and methods for learning sum-product networks.

The MN library reads, writes, and represents Markov networks with factors represented as tables, trees, sets of features, or individual features.