Yahoo!

About: Yahoo! is a company organization based out in London, United Kingdom. It is known for research contribution in the topics: Population & Web search query. The organization has 26749 authors who have published 29915 publications receiving 732583 citations. The organization is also known as: Yahoo! Inc. & Maudwen-Yahoo! Inc.

A rigorous and customizable framework for privacy

Abstract: In this paper we introduce a new and general privacy framework called Pufferfish. The Pufferfish framework can be used to create new privacy definitions that are customized to the needs of a given application. The goal of Pufferfish is to allow experts in an application domain, who frequently do not have expertise in privacy, to develop rigorous privacy definitions for their data sharing needs. In addition to this, the Pufferfish framework can also be used to study existing privacy definitions.We illustrate the benefits with several applications of this privacy framework: we use it to formalize and prove the statement that differential privacy assumes independence between records, we use it to define and study the notion of composition in a broader context than before, we show how to apply it to protect unbounded continuous attributes and aggregate information, and we show how to use it to rigorously account for prior data releases.

Multi-armed bandit problems with dependent arms

Abstract: We provide a framework to exploit dependencies among arms in multi-armed bandit problems, when the dependencies are in the form of a generative model on clusters of arms. We find an optimal MDP-based policy for the discounted reward case, and also give an approximation of it with formal error guarantee. We discuss lower bounds on regret in the undiscounted reward scenario, and propose a general two-level bandit policy for it. We propose three different instantiations of our general policy and provide theoretical justifications of how the regret of the instantiated policies depend on the characteristics of the clusters. Finally, we empirically demonstrate the efficacy of our policies on large-scale real-world and synthetic data, and show that they significantly outperform classical policies designed for bandits with independent arms.

Simrank++: query rewriting through link analysis of the click graph

Abstract: We focus on the problem of query rewriting for sponsored search. We base rewrites on a historical click graph that records the ads that have been clicked on in response to past user queries. Given a query q, we first consider Simrank [7] as a way to identify queries similar to q, i.e., queries whose ads a user may be interested in. We argue that Simrank fails to properly identify query similarities in our application, and we present two enhanced versions of Simrank: one that exploits weights on click graph edges and another that exploits "evidence." We experimentally evaluate our new schemes against Simrank, using actual click graphs and queries from Yahoo!, and using a variety of metrics. Our results show that the enhanced methods can yield more and better query rewrites.

Threshold conditions for arbitrary cascade models on arbitrary networks

Abstract: Given a network of who-contacts-whom or who-links-to-whom, will a contagious virus/product/meme spread and ‘take over’ (cause an epidemic) or die out quickly? What will change if nodes have partial, temporary or permanent immunity? The epidemic threshold is the minimum level of virulence to prevent a viral contagion from dying out quickly and determining it is a fundamental question in epidemiology and related areas. Most earlier work focuses either on special types of graphs or on specific epidemiological/cascade models. We are the first to show the G2-threshold (twice generalized) theorem, which nicely de-couples the effect of the topology and the virus model. Our result unifies and includes as special case older results and shows that the threshold depends on the first eigenvalue of the connectivity matrix, (a) for any graph and (b) for all propagation models in standard literature (more than 25, including H.I.V.). Our discovery has broad implications for the vulnerability of real, complex networks and numerous applications, including viral marketing, blog dynamics, influence propagation, easy answers to ‘what-if’ questions, and simplified design and evaluation of immunization policies. We also demonstrate our result using extensive simulations on real networks, including on one of the biggest available social-contact graphs containing more than 31 million interactions among more than 1 million people representing the city of Portland, Oregon, USA.

Suggesting contacts for social networks

Abstract: A social network is managed by applying connectivity and similarity measures to social network information to identify possible new relationships between social network users, and then automatically suggest those identified relationships to the social network users. The social network information can include user profile information and indicate existing social relationships between the users in the social network. Users can provide feedback regarding the suggestions, including indications whether the relationship was accepted, consummated, or declined. The social network information can be updated using the feedback. Similarity measures can be based on one or more of shared contacts, or common interests or activities, or content associated with social network users, or ratings within the social network of users and/or their content. Possible relationships having similarity measures that suggest the users likely to already know each other, can be omitted and not suggested.