Publications by Karl Aberer | EPFL Graph Search

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The database and information retrieval communities have long been recognized as being irreconcilable. Today, however, we witness a surprising convergence of the techniques used by both communities in decentralized, large-scale environments. The newly emerging field of reputation based trust management, borrowing techniques from both communities, best demonstrates this claim. We argue that incomplete knowledge and increasing autonomy of the participating entities are the driving forces behind this convergenc

Twitter is a micro-blogging service on the Web, where people can enter short messages, which then become visible to other users of the service. While the topics of these messages varies, there are a lot of messages where the users express their opinions ab ...

Reputation is a well established means to determine trustworthiness in online systems in various contexts, e.g. online transactions, product recommendation, e-mail spam fighting, etc. However, typically these reputation systems are "closed" outside of the ...

The availability of cheap and smart wireless sensing devices provides unprecedented possibilities to monitor the physical world. On the technical side these devices introduce several original research problems, many of them related to the integration of the rampant technology proposals. Global Sensor Network (GSN) is a platform which provides a scalable infrastructure for integrating heterogeneous sensor network technologies using a small set of powerful abstractions. GSN supports the integration and discov

Both sensor coverage maximization and energy cost minimization are the fundamental requirements in the design of real-life mobile sensing applications, e.g., (1) deploying environ- mental sensors (like CO2, fine particle measurement) on public transports t ...

Lots of machine learning models with applications in Multimedia Search are released as Open Source Software. However, integrating these models into an application is not always an easy task due to the lack of a consistent interface to run, train or distrib ...

Advanced applications for Distributed Hash Tables (DHTs), such as Peer-to-Peer Information Retrieval, require a DHT to quickly and efficiently process a large number (in the order of millions) of requests. In this paper we study mechanisms to optimize the ...

P-Grid is a decentralized DHT-based peer-to-peer system with logarithmic search complexity. As it is intended to provide a platform for distributed information management beyond mere file-sharing it supports an update functionality with lazy consistency guarantees, identity management disentangling the DHT from the underlying networking infrastructure, and decentralized load balancing. In this paper we first give a brief overview of the theoretical foundations of P-Grid and the supporting functionalities. T

A growing amount of data is produced daily resulting in a growing demand for storage solutions. While cloud storage providers offer a virtually infinite storage capacity, data owners seek geographical and provider diversity in data placement, in order to a ...

Applying classical time-series analysis techniques to online content is challenging, as web data tends to have data quality issues and is often incomplete, noisy, or poorly aligned. In this paper, we tackle the problem of predicting the evolution of a time ...

Many schemes have been recently advanced for storing data on multiple clouds. Distributing data over different cloud storage providers (CSPs) automatically provides users with a certain degree of information leakage control, as no single point of attack can leak all user's information. However, unplanned distribution of data chunks can lead to high information disclosure even while using multiple clouds. In this paper, to address this problem we present StoreSim, an information leakage aware storage system

People readily express their opinions about the various products, companies, TV shows etc., on Twitter. These tweet messages are thus a rich source of information that can be exploited to understand the sentiments about the concerned products or services. ...

There has been an increasing research interest in developing full-text retrieval based on peer-to-peer (P2P) technology. So far, these research efforts have largely concentrated on efficiently distributing an index. However, ranking of the results retrieve ...

The Internet has become an important source of information that significantly affects social, economical and political life. The content available in the Web is the basis for the operation of the digital economy. Moreover, Web content has become essential ...

As sensors continue to proliferate, the capabilities of effectively querying not only sensor data but also its metadata becomes important in a wide range of applications. This paper demonstrates a search system that utilizes various techniques and tools fo ...

We study the problem of continuous monitoring of top-k queries over multiple non-synchronized streams. Assuming a sliding window model, this general problem has been a well addressed research topic in recent years. However, most approaches assume the strea ...

We present HAMLET, a suite of principles, scoring models and algorithms to automatically propagate metadata along edges in a document neighborhood. As a showcase scenario we consider tag prediction in community-based Web 2.0 tagging applications. Experimen ...

Social media is becoming more and more integrated in the distribution and consumption of news. How is news in social media different from mainstream news? % This paper presents a comparative analysis covering a span of 17 months and hundreds of news events ...

The amount of controversial issues being discussed on the Web has been growing dramatically. In articles, blogs, and wikis, people express their points of view in the form of arguments, i.e., claims that are supported by evidence. Discovery of arguments ha ...

Federated learning (FL) has recently emerged as a compelling machine learning paradigm, prioritizing the protection of privacy for training data. The increasing demand to address issues such as "the right to be forgotten" and combat data poisoning attacks ...

Karl Aberer

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On the Convergence of Structured Search, Information Retrieval and Trust Management in Distributed Systems

What have fruits to do with technology? The case of Orange, Blackberry and Apple

Synergies of different reputation systems: challenges and opportunities

Global Sensor Networks

OptiMoS: Optimal Sensing for Mobile Sensors

MoZuMa: A Model Zoo for Multimedia Applications

Improving the Throughput of Distributed Hash Tables Using Congestion-Aware Routing

Experimental evaluation results of an advanced DHT-based peer-to-peer system

Scalia: An Adaptive Scheme for Efficient Multi-Cloud Storage

Predicting the Success of Online Petitions Leveraging Multidimensional Time-Series

StoreSim: Optimizing Information Leakage in Multicloud Storage Services

TweetSpector: Entity-based retrieval of Tweets

Aggregation of a Term Vocabulary for Peer-to-Peer Information Retrieval: a DHT Stress Test

Studying Web Content Credibility by Social Simulation

Advanced Search, Visualization and Tagging of Sensor Metadata

Evaluating Top-k Queries over Incomplete Data Streams

To Tag or Not to Tag ? Harvesting Adjacent Metadata in Large-Scale Tagging Systems

Comparing Events Coverage in Online News and Social Media: The Case of Climate Change

Argument discovery via crowdsourcing

Fast-FedUL: A Training-Free Federated Unlearning with Provable Skew Resilience