Publications de Karl Aberer | EPFL Graph Search

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Peer-To-Peer systems are driving a major paradigm shift in the era of genuinely distributed computing. Gnutella is a good exam- ple of a Peer-To-Peer success story: a rather simple software enables Internet users to freely exchange files, such as MP3 music files. But it shows up also some of the limitations of current P2P information sys- tems with respect to their ability to manage data efficiently. In this paper we introduce P-Grid, a scalable access structure that is specifically de- signed for Peer-To-P

Air pollution is one of the key indicators for quality of life in urban environments, and is also the subject of global health concern, given the number of mortal diseases associated to exposure to pollutants. Assessing and monitoring air quality is an imp ...

The availability of massive volumes of data and recent advances in data collection and processing platforms have motivated the development of distributed machine learning algorithms. In numerous real-world applications large datasets are inevitably noisy a ...

One fundamental issue in existing reputation mechanisms, particularly those in open and decentralized multi-agent systems, is whitewashing attacks by rational providers. If identities are cheap, it is beneficial for a provider to simply defect when selling ...

We tackle the problem of disambiguating entities on the Web. We propose a user-driven scheme where graphs of entities -- represented by globally identifiable declarative artifacts -- self-organize in a dynamic and probabilistic manner. Our solution has the ...

Demand response (DR) emerges as one of the cheapest and greenest solutions to match supply and demand in the electricity sector. Compared to price-based DR, incentive-based DR is considered to be more promising, since it does not require consumers to monitor price fluctuation (which often considered as an additional burden). In addition, it allows utility companies to design more attractive and customized incentives to encourage consumer participation in DR events. While DR has been focused on large and ind

Web search engines designed on top of peer-to-peer (P2P) overlay networks show promise to enable attractive search scenarios operating at a large scale. However the design of effective indexing techniques for extremely large document collections still raises a number of open technical challenges. Resource sharing, self-organization, and low maintenance costs are favorable properties of P2P overlays in the perspective of large-scale search, but we also face new problems due to potentially huge bandwidth cons

Online debates provide critical insights into public opinion and societal trends, yet the unstructured nature of these discussions presents significant challenges for analysis. In this paper, we present SAGESSE, a novel argumentation parsing pipeline tailo ...

This paper focuses on replication in DHT based structured overlay networks, and presents a theoretical framework for optimal replication in such networks with respect to query frequency. In particular, we determine the optimal replication factor for query-adaptive load balancing, and a topology specific placement strategy for an important class of DHT networks. We also provide a taxonomy of replication strategies in existing systems, discussing them with respect to this optimal scheme, and sketch further is

This paper provides a quantative comparison of the efficiency of the self-organized construction processes of the P-Grid and FreeNet peer-to-peer systems. Starting from a defined, realistic network topology we simulate the construction of their access structures and measure the incurred message load and memory usage for routing tables. Besides these results our experimental setup may also be used as a starting point for defining a standard test and evaluation suite for P2P systems.

With the price of wireless sensor technologies diminishing rapidly we can expect large numbers of autonomous sensor networks being deployed in the near future. These sensor networks will typically not remain isolated but the need of interconnecting them on ...

Automatizing information commerce requires languages to represent the typical information commerce processes. Existing languages and standards cover either only very specific types of business models or are too general to capture in a concise way the specific properties of information commerce processes. We introduce a language that is specifically designed for information commerce. It can be directly used for the implementation of the processes and communication required in information commerce. It allows

Graph neural networks take node features and graph structure as input to build representations for nodes and graphs. While there are a lot of focus on GNN models, understanding the impact of node features and graph structure to GNN performance has received ...

We consider K-Nearest Neighbor search for high dimensional data in large-scale structured Peer-to-Peer networks. We present an efficient mapping scheme based on p-stable Locality Sensitive Hashing to assign hash buckets to peers in a Chord-style overlay ne ...

Computing statistical measures for large databases of time series is a fundamental primitive for querying and mining time-series data [1]–[6]. This primitive is gaining importance with the increasing number and rapid growth of time series databases. In thi ...

Infinite nature of sensor data poses a serious challenge for query processing even in a cloud infrastructure. Model-based sensor data approximation reduces the amount of data for query processing, but all modeled segments need to be scanned, in the worst c ...

We propose a semi-automated method for redeploying bioinformatic databases indexed in a Web portal as a decentralized, semantically integrated and service-oriented Data Grid. We generate peer-to-peer schema mappings leveraging on cross-referenced instances ...

In this paper we present a hybrid model for real-time query processing over data stream collected by mobile air quality sensors. First, we introduce a novel indexing scheme for representing air quality and use it for generating and evaluating a static mode ...

Karl Aberer

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P-Grid: A self-organizing access structure for P2P information systems

Semantic Data Layers in Air Quality Monitoring for Smarter Cities

Efficient Distributed Decision Trees for Robust Regression

Using identity premium for cooperation enforcement and whitewashing prevention in rational environments

idMesh: graph-based disambiguation of linked data

Characterizing the Optimal Incentives for Pervasive Demand Response

Building a peer-to-peer full-text Web search engine with highly discriminative keys

SAGESSE: A System for Argument Generation, Extraction and Structuring of Social Exchanges

Principles of Query-Adaptive Optimal Replication in DHTs

Self-organized construction of distributed access structures: A comparative evaluation of P-Grid and FreeNet

Infrastructure for data processing in large-scale interconnected sensor networks

A language for information commerce processes

Self-organized construction of distributed access structures: A comparative evaluation of P-Grid and FreeNet

A Language for Information Commerce Processes

Nature vs. Nurture: Feature vs. Structure for Graph Neural Networks

LSH At Large - Distributed KNN Search in High Dimensions

A FFINITY: Efficiently Querying Statistical Measures on Time-Series Data

Model-View Sensor Data Management in the Cloud

From Bioinformatic Web Portals to Semantically Integrated Data Grid Networks

A model-based back-end for air quality data management