2015 Informs Annual Meeting

WB24

INFORMS Philadelphia – 2015

WB24 24-Room 401, Marriott Joint Session AI/ICS: Decision Diagrams for Optimization and Artificial Intelligence Sponsor: Artificial Intelligence and ICS Sponsored Session Chair: Andre Augusto Cire, Assistant Professor, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada, acire@utsc.utoronto.ca 1 - Consistency as Projection John Hooker, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA, 15213, United States of America, jh38@andrew.cmu.edu We interpret various forms of consistency in constraint programming as projection and propose a new form of consistency, J-consistency, that is achieved by projecting the constraint set onto a subset J of variables. We show how J- consistency can reduce backtracking when constraints are propagated through decision diagrams. We introduce J-consistency algorithms for SAT, among, sequence, regular, and alldiff constraints. 2 - Decision Diagram Decomposition of Optimization Problems David Bergman, David.Bergman@business.uconn.edu, Andre Augusto Cire Decision diagrams (DDs) can be used to compactly represent solutions to optimization problems, but the representation grows exponentially large in general, prohibiting their direct application. However, it is often the case that the diagram has limited size when representing the solution set for a substructure of a given problem. In this talk we discuss how DDs can be used when a problem decomposes in such a way that each individual portion has a limited-size DD. 3 - Decision Diagrams for Efficient Inference and Optimization in Expressive Continuous Domains I will introduce the XADD — an extension of the algebraic decision diagram to continuous variables — and show how to define and efficiently compute elementary arithmetic operations, integrals, and maximization for various restrictions of these functions. I will then cover a range of applications where the XADD has yielded novel closed-form solutions: (a) structured probabilistic inference, (b) parametric constrained optimization, and (c) sequential decision- making problems. 4 - Sentential Decision Diagrams and their Applications Adnan Darwiche, UCLA, 4532-D Boelter Hall, Los Angeles, CA, 90095-1596, United States of America, darwiche@cs.ucla.edu, Guy Van Den Broeck, Arthur Choi Sentential decision diagrams (SDDs) are a new class of decision diagrams that branch on arbitrary sentences instead of individual variables. They generalize ordered binary decision diagrams (OBDDs) and carry over many desirable OBDD properties, such as canonicity and support for bottom-up compilation with Boolean operators, while being more compact than OBDDs. These key properties have enabled several successful AI applications in recent years, particularly for reasoning about uncertainty. Scott Sanner, Asst. Professor, Oregon State University, 1148 Kelley Engineering Center, Corvallis, OR, 97331, United States of America, ssanner@gmail.com

2 - What Makes Geeks Tick? A Study of Stack Overflow Careers Tingting Nian, NYU Stern, 44 West 4th Street, New York, NY, 10012, United States of America, tnian@stern.nyu.edu, Luis Cabral, Lei Xu We study user contributions to Stack Overflow, the largest online programmers community. Using a diff-in-diff approach, we show that the event of finding a new job implies a reduction of 25% in reputation-generating activity, but only a reduction of 8% in non-reputation-generating activity. We consider a series of robustness tests to tease out alternative explanations for these variations; together, the results suggest that career concerns play an important role in explaining user contributions. 3 - Sentiment Manipulation in Online Platforms and Opinion Forums: A Regression Discontinuity Approach Shun-yang Lee, University of Texas at Austin, Austin, TX, United States of America, shunyang.lee@utexas.edu, Andrew Whinston, Liangfei Qiu Online platforms are prone to abuse and manipulations from strategic parties. We characterize strategic firms’ manipulation incentives through in a rational expectation equilibrium framework (REE), and conduct empirical analysis on a Twitter data set through a regression discontinuity design (RDD) approach. We find that both the average Twitter sentiment and the proportion of highly positive tweets exhibit a significant drop on the movie’s release day, suggesting firms’ strategic manipulation. 4 - Open Platform Ecosystem Dynamics and System Efficiency with Advertising Investment

Gou Qinglong, Associate Professor, University of Science & Technology of China, No.96, JinZhai Road Baohe District, Hefei, China, tslg@ustc.edu.cn, Ruibing Wang, Yonghua Ji

We utilize a dynamic model to explore the advertising strategies for an open platform ecosystem where the platform and app are to determine their advertising efforts. We find that a transfer payment can improve system efficiency significantly.

WB26 26-Room 403, Marriott Production and Scheduling III Contributed Session

Chair: Alejandro MacCawley, Assistant Professor, P. Universidad Catolica de Chile, Vicuna Mackenna 4860 Macul, Santiago, 7820436, Chile, amac@ing.puc.cl 1 - Minimizing Demand Oriented Maintenance Cost Marcus Poggi, PUC-Rio Informatica, Rua Marquís de São Vicente, 225, Gávea, Rio de Janeiro, Brazil, poggi@inf.puc-rio.br, Ivan Lima In a production environment, machines fail with a given probability, function of its operating time since last maintenance. Facing a demand scenario for a planning horizon, one is interested in estimating the efficient frontier for maintenance cost and risk of not fulfilling a demand SLA. This stochastic problem with endogenous uncertainty is modeled over a discrete space-time network. Heuristic and exact approaches are devised. 2 - Minimizing Working Capital Requirements in a Dynamic Lot Sizing Model with Infinite Capacity Thomas Yeung, Associate Professor, Ecole des Mines de Nantes, 4 Rue Alfred Kastler, BP20722, Nantes, 44307, France, thomas.yeung@mines-nantes.fr, Nathalie Bostel, David Lemoine, Yuan Bian Traditional tactical production planning models do not consider a minimum financial need in terms of working capital requirements (WCR) to maintain operations. We introduce a first link by proposing a new generic WCR model for the dynamic lot sizing problem with single-site/level/product and infinite capacity. We show that our model adheres to the zero-inventory ordering policy allowing an exact polynomial algorithm to be formulated. Numerical tests compare the results with traditional models. 3 - Minimizing Tardiness and Maintenance Costs in Flow Shop Scheduling using Lower-bound-based GA Andrew Yu, Associate Professor, The University of Tennessee, Industrial and Systems Engineering, Knoxville, TN, 37996, United States of America, ajyu@utk.edu, Javad Seif A permutation flow shop scheduling problem is reformulated as a mixed-integer linear program after incorporating flexible and diverse maintenance activities for minimizing tardiness and maintenance costs. The MILP model is NP-hard for a large size of problem. Thus a lower-bound based genetic algorithm is developed. The algorithm is further tuned using design experiment to control and determine the GA parameters.

WB25 25-Room 402, Marriott Economics of Information Systems Sponsor: Information Systems Sponsored Session

Chair: Liangfei Qiu, Assistant Professor, University of Florida, Department of ISOM, Gainesville, FL, United States of America, liangfeiqiu@ufl.edu 1 - Cross-market Integration and Sabotage Hong Guo, University of Notre Dame, 356 Mendoza College of Business, Notre Dame, IN, 46556, United States of America, hguo@nd.edu, Yabing Jiang, Asoo Vakharia, Arthur Lim Recent industry developments motivate the study of cross-market firm integrations, which often raises controversies and regulatory concerns due to the potential negative effects through the integrated firms’ sabotage activities. In this paper, we analyze integrations of firms in two interrelated markets and the integrated firm’s incentive to sabotage its rival in both markets. Our findings provide important managerial and policy implications for cross-market firm integrations.

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