Ranked Retrieval in Uncertain and Probabilistic Databases

Ranking queries are widely used in data exploration, data analysis and decision making scenarios. While most of the currently proposed ranking techniques focus on deterministic data, several emerging applications involve data that are imprecise or uncertain. Ranking uncertain data raises new challenges in query semantics and processing, making conventional methods inapplicable. Furthermore, the interplay between ranking and uncertainty models introduces new dimensions for ordering query results that do not exist in the traditional settings. This dissertation introduces new formulations and processing techniques for ranking queries on uncertain data. The formulations are based on marriage of traditional ranking semantics with possible worlds semantics under widely-adopted uncertainty models. In particular, we focus on studying the impact of tuple-level and attribute-level uncertainty on the semantics and processing techniques of ranking queries. Under the tuple-level uncertainty model, we introduce a processing framework leveraging the capabilities of relational database systems to recognize and handle data uncertainty in score-based ranking. The framework encapsulates a state space model, and efficient search algorithms that compute query answers by lazily materializing the necessary parts of the space. Under the attribute-level uncertainty model, we give a new probabilistic ranking model, based on partial orders, to encapsulate the space of possible rankings originating from uncertainty in attribute values. We present a set of efficient query evaluation algorithms, including sampling-based techniques based on the theory of Markov chains and Monte-Carlo method, to compute query answers. We build on our techniques for ranking under attribute-level uncertainty to support rank join queries on uncertain data. We show how to extend current rank join methods to handle uncertainty in scoring attributes. We provide a pipelined query operator implementation of uncertainty-aware rank join algorithm integrated with sampling techniques to compute query answers

Not It: Opting out of Voluntary Coalitions that Provide a Public Good

Most coalitions that form to increase contributions to a public good do not require full participation by all users of the public good, and therefore create incentives for free riding. If given the opportunity to opt out of a voluntary coalition, in theory, agents should try to be among the first to do so, forcing the remaining undecided agents to bear the cost of participating in the coalition. This study tests the predicted sequence of participation decisions in voluntary coalitions using real-time threshold public goods experiments. We find that subjects’ behavior is more consistent with the theoretical predictions when the difference in payoffs between coalition members and free-riding non-members is relatively large. Key Words: voluntary coalitions, voluntary agreements, public goods experiments, free riding

Positive Logic with Adjoint Modalities: Proof Theory, Semantics and Reasoning about Information

We consider a simple modal logic whose non-modal part has conjunction and disjunction as connectives and whose modalities come in adjoint pairs, but are not in general closure operators. Despite absence of negation and implication, and of axioms corresponding to the characteristic axioms of (e.g.) T, S4 and S5, such logics are useful, as shown in previous work by Baltag, Coecke and the first author, for encoding and reasoning about information and misinformation in multi-agent systems. For such a logic we present an algebraic semantics, using lattices with agent-indexed families of adjoint pairs of operators, and a cut-free sequent calculus. The calculus exploits operators on sequents, in the style of "nested" or "tree-sequent" calculi; cut-admissibility is shown by constructive syntactic methods. The applicability of the logic is illustrated by reasoning about the muddy children puzzle, for which the calculus is augmented with extra rules to express the facts of the muddy children scenario.Comment: This paper is the full version of the article that is to appear in the ENTCS proceedings of the 25th conference on the Mathematical Foundations of Programming Semantics (MFPS), April 2009, University of Oxfor

Toward Entity-Aware Search

As the Web has evolved into a data-rich repository, with the standard "page view," current search engines are becoming increasingly inadequate for a wide range of query tasks. While we often search for various data "entities" (e.g., phone number, paper PDF, date), today's engines only take us indirectly to pages. In my Ph.D. study, we focus on a novel type of Web search that is aware of data entities inside pages, a significant departure from traditional document retrieval. We study the various essential aspects of supporting entity-aware Web search. To begin with, we tackle the core challenge of ranking entities, by distilling its underlying conceptual model Impression Model and developing a probabilistic ranking framework, EntityRank, that is able to seamlessly integrate both local and global information in ranking. We also report a prototype system built to show the initial promise of the proposal. Then, we aim at distilling and abstracting the essential computation requirements of entity search. From the dual views of reasoning--entity as input and entity as output, we propose a dual-inversion framework, with two indexing and partition schemes, towards efficient and scalable query processing. Further, to recognize more entity instances, we study the problem of entity synonym discovery through mining query log data. The results we obtained so far have shown clear promise of entity-aware search, in its usefulness, effectiveness, efficiency and scalability

Rich States, Poor States: ALEC-Laffer State Economic Competitiveness Index

Ranks states' business climates based on income, population growth, and employment and outlook based on current tax policies; analyzes their fiscal conditions; reviews 2010 fiscal reform initiatives; and recommends policies to spur economic growth

What Numbers to Choose for My Lottery Ticket? Behavior Anomalies in the Chinese Online Lottery Market

The Chinese Online Lottery provides field evidence of three anomalies. The first anomaly, which has previously not been documented when there is a financial incentive to overcome, is the guidance effect. Since the target game in this project is a pari-mutuel game, which means people will share the jackpot with other winners, the best strategy should be to choose the least popular numbers among others – information that people could obtain on the webpage. However, to my surprise, instead of doing so, people would choose the most popular numbers among others. The second anomaly tested is the gambler’s fallacy. Although it is proved that the gambler’s fallacy does exist, the influence lasts only three days, which is much shorter than prior research. Furthermore, the dataset’s availability makes it possible to show how the two fallacies unfold over time within a round. This was unlikely before the phenomenon of online betting. The result demonstrates that later entrants are subject to more fallacies than earlier ones. Finally, the paper adds to the evidence showing the additional, culturally contingent pull of special numbers. In China, bettors prefer to choose the lucky number 8, even it won the game in prior rounds, but they are reluctant to choose the unlucky number 14 even it has not been picked for a long while.Lottery Game, Gambler’s Fallacy, Guidance Effect, Number Culture

Fighting Income Tax Evasion with Positive Rewards: Experimental Evidence

This paper provides experimental evidence regarding the influence of positive rewards on income tax evasion behavior. In particular, we experimentally test the impact of positive rewards in form of individual lottery winnings for honest taxpayers. Among other things, we find that these positive rewards lead to a significantly higher rate of tax compliance. Moreover, there are two gender effects. Males not only evade taxes to a much higher extent than females, they also show a stronger positive response to the lottery scheme. This allows us to draw some interesting policy recommendations.