Uncertainty
The Incomplete Rosetta Stone Problem: Identifiability Results for Multi-View Nonlinear ICA
Gresele, Luigi, Rubenstein, Paul K., Mehrjou, Arash, Locatello, Francesco, Schölkopf, Bernhard
We consider the problem of recovering a common latent source with independent components from multiple views. This applies to settings in which a variable is measured with multiple experimental modalities, and where the goal is to synthesize the disparate measurements into a single unified representation. We consider the case that the observed views are a nonlinear mixing of component-wise corruptions of the sources. When the views are considered separately, this reduces to nonlinear Independent Component Analysis (ICA) for which it is provably impossible to undo the mixing. We present novel identifiability proofs that this is possible when the multiple views are considered jointly, showing that the mixing can theoretically be undone using function approximators such as deep neural networks. In contrast to known identifiability results for nonlinear ICA, we prove that independent latent sources with arbitrary mixing can be recovered as long as multiple, sufficiently different noisy views are available.
The Kernel Interaction Trick: Fast Bayesian Discovery of Pairwise Interactions in High Dimensions
Agrawal, Raj, Huggins, Jonathan H., Trippe, Brian, Broderick, Tamara
Discovering interaction effects on a response of interest is a fundamental problem faced in biology, medicine, economics, and many other scientific disciplines. In theory, Bayesian methods for discovering pairwise interactions enjoy many benefits such as coherent uncertainty quantification, the ability to incorporate background knowledge, and desirable shrinkage properties. In practice, however, Bayesian methods are often computationally intractable for even moderate-dimensional problems. Our key insight is that many hierarchical models of practical interest admit a particular Gaussian process (GP) representation; the GP allows us to capture the posterior with a vector of O(p) kernel hyper-parameters rather than O(p^2) interactions and main effects. With the implicit representation, we can run Markov chain Monte Carlo (MCMC) over model hyper-parameters in time and memory linear in p per iteration. We focus on sparsity-inducing models and show on datasets with a variety of covariate behaviors that our method: (1) reduces runtime by orders of magnitude over naive applications of MCMC, (2) provides lower Type I and Type II error relative to state-of-the-art LASSO-based approaches, and (3) offers improved computational scaling in high dimensions relative to existing Bayesian and LASSO-based approaches.
Towards Interactive Causal Relation Discovery Driven by an Ontology
Munch, Melanie (University of Paris-Saclay) | Dibie, Juliette (University of Paris-Saclay) | Wuillemin, Pierre-Henri (Sorbonne University) | Manfredotti, Cristina (University of Paris-Saclay)
Discovering causal relations in a knowledge base represents nowadays a challenging issue, as it gives a brand new way of understanding complex domains. In this paper, we present a method to combine an ontology with an object-oriented extension of the Bayesian networks (BNs), called probabilistic relational model (PRM), in order to help a user to check his/her assumption on causal relations between data and to discover new relationships. This assumption is also important as it guides the PRM construction and provide a learning under causal constraints.
Relational Forward Backward Algorithm for Multiple Queries
Gehrke, Marcel (University of Lübeck) | Braun, Tanya (University of Lübeck) | Möller, Ralf (University of Lübeck)
The lifted dynamic junction tree algorithm (LDJT) efficiently answers filtering and prediction queries for probabilistic relational temporal models by building and then reusing a first-order cluster representation of a knowledge base for multiple queries and time steps. Specifically, this paper contributes (i) a relational forward backward algorithm with LDJT, (ii) smoothing for hindsight queries, and (iii) different approaches to instantiate a first-order cluster representation during a backward pass. Further, our relational forward backward algorithm makes hindsight queries with huge lags feasible. LDJT answers multiple temporal queries faster than the static lifted junction tree algorithm on an unrolled model, which performs smoothing during message passing.
Reliable Discretization of Deterministic Equations in Bayesian Networks
Antonucci, Alessandro (Istituto Dalle Molle di Studi sull’Intelligenza Artificiale)
We focus on the problem of modeling deterministic equations over continuous variables in discrete Bayesian networks. This is typically achieved by a discretization of both input and output variables and a degenerate quantification of the corresponding conditional probability tables. This approach, based on classical probabilities, cannot properly model the information loss induced by the discretization. We show that a reliable modeling of such epistemic uncertainty can be instead achieved by credal sets, i.e., convex sets of probability mass functions. This transforms the original Bayesian network in a credal network, possibly returning interval-valued inferences, that are robust with respect to the information loss induced by the discretisation. Algorithmic strategies for an optimal choice of the discretisation bins are also provided.
Influence-Based Independence
Özçep, Özgür L. (University of Lübeck) | Kuhr, Felix (University of Lübeck) | Möller, Ralf (University of Lübeck)
Conditional independence structures describe independencies of one set of variables from another set of variables conditioned upon a third set of variables. These structures are invaluable means for compact representations of knowledge because independencies can be exploited for useful factorizations. Conditional independence structures appear in different disguise in various areas of knowledge representation, be it the conditional independence of sets of random variables in probabilistic graphical models such as Bayesian networks or as conditional functions related to belief revision, or as in- dependencies induced by (embedded) multivalued dependencies in data bases. This paper investigates conditional independencies for Boolean functions using Fourier analysis. We define three notions of independence based on the notion of influence of a variable on a function and draw connections to multivalued dependencies.
Hierarchical Classification With Bayesian Networks and Chained Classifiers
Serrano-Pérez, Jonathan (Instituto Nacional de Astrofísica Óptica y Electrónica) | Sucar, Luis Enrique (Instituto Nacional de Astrofísica Óptica y Electrónica)
In this work is proposed a method for Hierarchical Classification, which takes advantage of the hierarchical structure to influence the prediction of local classifiers with their neighbors. To achieve this, two strategies are combined. The first is to represent the hierarchical structure as a Bayesian network, and the second is to build chained classifiers that feed the Bayesian network as local classifiers. The proposed method was tested in several datasets of functional genomics, which consist of tree-structured hierarchies. The results of several variants of the proposed method are compared to the standard methods, Flat and Top-Down, as well as with a start of the art technique, showing superior performance under several metrics.
Linear Time and Space Algorithm for Computing all the Fagin-Halpern Conditional Beliefs Generated From Consonant Belief Functions
Polpitiya, Lalintha G. (University of Miami) | Premaratne, Kamal (University of Miami) | Murthi, Manohar N. (University of Miami)
Halpern 1990; Smets 1991; Yu and Arasta 1994), Dempster's conditional and Fagin-Halpern (FH) conditional can be considered the most widely used two DST conditional The flexibility and expressiveness of Dempster-Shafer (DS) A widely used approach for carrying out precise computation theoretic models make DS evidence theory (Dempster 1967; of the Dempster's conditional is a matrix calculus 1968; Shafer 1976) an ideal framework for reasoning and based algorithm which generates the Dempster's conditional decision making under uncertainty in Artificial Intelligence masses (Klawonn and Smets 1992; Smets 2002). Therefore, this specialization matrix-based method imposes Computing the DST belief functions and the DST conditionals, a prohibitive burden when dealing with larger FoDs.
Learning Strategies for Resisting Power Attacks on Wi-Fi Direct Group Formation
Maraj, Arianit (Florida Institute of Technology) | Atkinson, Timothy (Florida Institute of Technology) | Silaghi, Marius C. (Florida Institute of Technology)
Attacks — on the recent Wi-Fi Direct standard developed for IoT devices — that exploit the high power consumption required for the group owner function are addressed here by introducing intelligent decision making into the group owner negotiation process. The Wi-Fi Direct standard was introduced with the intention of simplifying peer-to-peer connections in home applications while helping devices to save power by centralizing effort into a single group owner device negotiated on start-up. Attacks on the group formation stage can be based on manipulating a victim device to frequently end up being assigned the group owner function, thereby depleting its batteries at faster rates than its peer devices. This manipulation is made easy by the group formation process adopted by the standard. We propose to enhance the group formation process with secure features ensuring fairness by relying on commitments and learning about the behavior observed for peer devices in the past. Simulations are used to quantify the resistance achieved against several attack strategies.
Output-Constrained Bayesian Neural Networks
Yang, Wanqian, Lorch, Lars, Graule, Moritz A., Srinivasan, Srivatsan, Suresh, Anirudh, Yao, Jiayu, Pradier, Melanie F., Doshi-Velez, Finale
Bayesian neural network (BNN) priors are defined in parameter space, making it hard to encode prior knowledge expressed in function space. We formulate a prior that incorporates functional constraints about what the output can or cannot be in regions of the input space. Output-Constrained BNNs (OC-BNN) represent an interpretable approach of enforcing a range of constraints, fully consistent with the Bayesian framework and amenable to black-box inference. We demonstrate how OC-BNNs improve model robustness and prevent the prediction of infeasible outputs in two real-world applications of healthcare and robotics.