Engel, Yagil
Posted Prices Exchange for Display Advertising Contracts
Engel, Yagil (Microsoft Research) | Tennenholtz, Moshe (Microsoft Research)
We propose a new market design for display advertising contracts, based on posted prices. Our model and algorithmic framework address several major challenges: (i) the space of possible impression types is exponential in the number of attributes, which is typically large, therefore a complete price space cannot be maintained; (ii) advertisers are usually unable or reluctant to provide extensive demand (willingness-to-pay) functions, (iii) the levels of detail with which supply and demand are specified are often not identical.
Planning for Operational Control Systems with Predictable Exogenous Events
Brafman, Ronen (Ben-Gurion University of the Negev) | Domshlak, Carmel (Technion - Israel Institute of Technology) | Engel, Yagil (IBM Research) | Feldman, Zohar (IBM Research)
Various operational control systems (OCS) are naturally modeled as Markov Decision Processes. OCS often enjoy access to predictions of future events that have substantial impact on their operations. For example, reliable forecasts of extreme weather conditions are widely available, and such events can affect typical request patterns for customer response management systems, the flight and service time of airplanes, or the supply and demand patterns for electricity. The space of exogenous events impacting OCS can be very large, prohibiting their modeling within the MDP; moreover, for many of these exogenous events there is no useful predictive, probabilistic model. Realtime predictions, however, possibly with a short lead-time, are often available. In this work we motivate a model which combines offline MDP infinite horizon planning with realtime adjustments given specific predictions of future exogenous events, and suggest a framework in which such predictions are captured and trigger real-time planning problems. We propose a number of variants of existing MDP solution algorithms, adapted to this context, and evaluate them empirically.
Decomposed Utility Functions and Graphical Models for Reasoning about Preferences
Brafman, Ronen I. (Ben Gurion University) | Engel, Yagil (Technion)
Recently, Brafman and Engel (2009) proposed new concepts of marginal and conditional utility that obey additive analogues of the chain rule and Bayes rule, which they employed to obtain a directed graphical model of utility functions that resembles Bayes nets. In this paper we carry this analogy a step farther by showing that the notion of utility independence, built on conditional utility, satisfies identical properties to those of probabilistic independence. This allows us to formalize the construction of graphical models for utility functions, directed and undirected, and place them on the firm foundations of Pearl and Paz's axioms of semi-graphoids. With this strong equivalence in place, we show how algorithms used for probabilistic reasoning such as Belief Propagation (Pearl 1988) can be replicated to reasoning about utilities with the same formal guarantees, and open the way to the adaptation of additional algorithms.
Transferable Utility Planning Games
Brafman, Ronen I. (Ben Gurion University) | Domshlak, Carmel (Technion) | Engel, Yagil (Technion) | Tennenholtz, Moshe (Microsoft R&D Center)
Connecting between standard AI planning constructs and a classical cooperative model of transferable-utility coalition games, we introduce the notion of transferable-utility (TU) planning games. The key representational property of these games is that coalitions are valued implicitly based on their ability to carry out efficient joint plans. On the side of the expressiveness, we show that existing succinct representations of monotonic TU games can be efficiently compiled into TU planning games. On the side of computation, TU planning games allow us to provide some of the strongest to date tractability results for core-existence and core-membership queries in succinct TU coalition games.