Multi-attribute decision making with weighted description logics

We introduce a decision-theoretic framework based on Description Logics (DLs), which can be used to encode and solve single stage multi-attribute decision problems. In particular, we consider the background knowledge as a DL knowledge base where each attribute is represented by a concept, weighted by a utility value which is asserted by the user. This yields a compact representation of preferences over attributes. Moreover, we represent choices as knowledge base individuals, and induce a ranking via the aggregation of attributes that they satisfy. We discuss the benefits of the approach from a decision theory point of view. Furthermore, we introduce an implementation of the framework as a Protégé plugin called uDecide. The plugin takes as input an ontology as background knowledge, and returns the choices consistent with the user’s (the knowledge base) preferences. We describe a use case with data from DBpedia. We also provide empirical results for its performance in the size of the ontology using the reasoner Konclude

The Term Structure of Interest Rates in a DSGE Model with Recursive Preferences

We solve a dynamic stochastic general equilibrium (DSGE) model in which the representative household has Epstein and Zin recursive preferences. The parameters governing preferences and technology are estimated by means of maximum likelihood using macroeconomic data and asset prices, with a particular focus on the term structure of interest rates. We estimate a large risk aversion, an elasticity of intertemporal substitution higher than one, and substantial adjustment costs. Furthermore, we identify the tensions within the model by estimating it on subsets of these data. We conclude by pointing out potential extensions that might improve the model’s fit.DSGE models, Epstein-Zin preferences, likelihood estimation, yield curve

Efficient estimation of statistical functions while preserving client-side privacy

Aggregating service users’ personal data for analytical purposes is a common practice in today’s Internet economy. However, distrust in the data aggregator, data breaches and risks of subpoenas pose significant challenges in the availability of data. The framework of differential privacy is enjoying wide attention due to its scalability and rigour of privacy protection it provides, and has become a de facto standard for facilitating privacy preserving information extraction. In this dissertation, we design and implement resource efficient algorithms for three fundamental data analysis primitives, marginal, range, and count queries while providing strong differential privacy guarantees. The first two queries are studied in the strict scenario of untrusted aggregation (aka local model) in which the data collector is allowed to only access the noisy/perturbed version of users’ data but not their true data. To the best of our knowledge, marginal and range queries have not been studied in detail in the local setting before our works. We show that our simple data transfomation techniques help us achieve great accuracy in practice and can be used for performing more interesting analysis. Finally, we revisit the problem of count queries under trusted aggregation. This setting can also be viewed as a relaxation of the local model called limited precision local differential privacy. We first discover certain weakness in a well-known optimization framework leading to solutions exhibiting pathological behaviours. We then propose more constraints in the framework to remove these weaknesses without compromising too much on utility

Cryptographic Foundations For Control And Optimization: Making Cloud-Based And Networked Decisions On Encrypted Data

Advances in communication technologies and computational power have determined a technological shift in the data paradigm. The resulting architecture requires sensors to send local data to the cloud for global processing such as estimation, control, decision and learning, leading to both performance improvement and privacy concerns. This thesis explores the emerging field of private control for Internet of Things, where it bridges dynamical systems and computations on encrypted data, using applied cryptography and information-theoretic tools.Our research contributions are privacy-preserving interactive protocols for cloud-outsourced decisions and data processing, as well as for aggregation over networks in multi-agent systems, both of which are essential in control theory and machine learning. In these settings, we guarantee privacy of the data providers\u27 local inputs over multiple time steps, as well as privacy of the cloud service provider\u27s proprietary information. Specifically, we focus on (i) private solutions to cloud-based constrained quadratic optimization problems from distributed private data; (ii) oblivious distributed weighted sum aggregation; (iii) linear and nonlinear cloud-based control on encrypted data; (iv) private evaluation of cloud-outsourced data-driven control policies with sparsity and low-complexity requirements. In these scenarios, we require computational privacy and stipulate that each participant is allowed to learn nothing more than its own result of the computation. Our protocols employ homomorphic encryption schemes and secure multi-party computation tools with the purpose of performing computations directly on encrypted data, such that leakage of private information at the computing entity is minimized. To this end, we co-design solutions with respect to both control performance and privacy specifications, and we streamline their implementation by exploiting the rich structure of the underlying private data

The Term Structure of Interest Rates in a DSGE Model With Recursive Preferences

A dynamic stochastic general equilibrium (DSGE) model in which households have Epstein and Zin recursive preferences is solved with perturbation. The parameters governing preferences and technology are estimated by maximum likelihood using macroeconomic data and the term structure of interest rates. The estimates imply a large risk aversion, an elasticity of intertemporal substitution higher than one, and substantial adjustment costs. Furthermore, the paper identifies the tensions within the model by estimating it on subsets of these data. The analysis concludes by pointing out potential extensions that may improve the model\u27s fit