8 research outputs found
A Logical Characterization of Constraint-Based Causal Discovery
We present a novel approach to constraint-based causal discovery, that takes
the form of straightforward logical inference, applied to a list of simple,
logical statements about causal relations that are derived directly from
observed (in)dependencies. It is both sound and complete, in the sense that all
invariant features of the corresponding partial ancestral graph (PAG) are
identified, even in the presence of latent variables and selection bias. The
approach shows that every identifiable causal relation corresponds to one of
just two fundamental forms. More importantly, as the basic building blocks of
the method do not rely on the detailed (graphical) structure of the
corresponding PAG, it opens up a range of new opportunities, including more
robust inference, detailed accountability, and application to large models
Marginal log-linear parameters for graphical Markov models
Marginal log-linear (MLL) models provide a flexible approach to multivariate
discrete data. MLL parametrizations under linear constraints induce a wide
variety of models, including models defined by conditional independences. We
introduce a sub-class of MLL models which correspond to Acyclic Directed Mixed
Graphs (ADMGs) under the usual global Markov property. We characterize for
precisely which graphs the resulting parametrization is variation independent.
The MLL approach provides the first description of ADMG models in terms of a
minimal list of constraints. The parametrization is also easily adapted to
sparse modelling techniques, which we illustrate using several examples of real
data.Comment: 36 page
Learning Topic Models and Latent Bayesian Networks Under Expansion Constraints
Unsupervised estimation of latent variable models is a fundamental problem
central to numerous applications of machine learning and statistics. This work
presents a principled approach for estimating broad classes of such models,
including probabilistic topic models and latent linear Bayesian networks, using
only second-order observed moments. The sufficient conditions for
identifiability of these models are primarily based on weak expansion
constraints on the topic-word matrix, for topic models, and on the directed
acyclic graph, for Bayesian networks. Because no assumptions are made on the
distribution among the latent variables, the approach can handle arbitrary
correlations among the topics or latent factors. In addition, a tractable
learning method via optimization is proposed and studied in numerical
experiments.Comment: 38 pages, 6 figures, 2 tables, applications in topic models and
Bayesian networks are studied. Simulation section is adde
Towards characterizing Markov equivalence classes for directed acyclic graphs with latent variables
Proceedings of the 21st Conference on Uncertainty in Artificial Intelligence, UAI 200510-1