ALEXANDRIA – Temporal Retrieval, Exploration and Analytics in Web archives – Asking Humans for Help

by prof. Wolfgang Nejdl, L3S Research Center

April 29th 2015 @ 16:00, in Room Levico

In this invited talk prof. Wolfgang Nejdl will present his work about

ALEXANDRIA — Temporal Retrieval, Exploration and Analytics in Web archives — “Asking Humans for Help”


The Web is one of the most important socio-technical systems of our time, mirroring trivia and popular culture, propaganda and politics, literature and high culture. Yet we have only very limited capabilities for accessing and exploring the past of the Web, in stark contrast to what we could learn from it.

Within ALEXANDRIA, we want to provide at least some of the tools enabling us to analyze the past, based on what is and what was available on the Web. Our goal in ALEXANDRIA is to significantly advance semantic and time-based indexing for Web archives using human-compiled knowledge available on the Web, to efficiently index, retrieve and explore information about entities and events from the past. We will further investigate mixed crowd- and machine-based Web analytics to support long-running and collaborative retrieval and analysis processes on Web archives.

In this talk I will focus on our recent research on crowd-based aspects, and specifically talk about how we can use human input for providing information about events, as well as about how to better ask for human help on crowdsourcing platforms.


Prof. Nejdl heads the L3S Research Center as well as the Distributed Systems Institute / Knowledge Based Systems.

Prof. Dr. Wolfgang Nejdl (born 1960) has been full professor of computer science at the University of Hannover since 1995. He received his M.Sc. (1984) and Ph.D. degree (1988) at the Technical University of Vienna, was assistant professor in Vienna from 1988 to 1992, and associate professor at the RWTH Aachen from 1992 to 1995. He worked as visiting researcher / professor at Xerox PARC, Stanford University, University of Illinois at Urbana-Champaign, EPFL Lausanne, and at PUC Rio.

Prof. Nejdl heads the L3S Research Center,, as well as the Distributed Systems Institute / Knowledge Based Systems, and does research in the areas of search and information retrieval, information systems, data mining and recommender systems, semantic web technologies and digital libraries. Recent projects in the L3S context include the EU projects ARCOMEM and ForgetIT, investigating Web and organization archive management and advanced search in such archives, the EU project CUBRIK, developing algorithms and systems for human-enhanced time-aware multimedia search, and Qualimaster, focusing on real time data stream analytics. He has just started an ERC Advanced Grant, ALEXANDRIA, to work on foundations for temporal retrieval, exploration and analytics in Web archives.

Wolfgang Nejdl published more than 330 scientific articles, as listed at DBLP, and has been program chair, program committee and editorial board member of numerous international conferences and journals, most recently including the role of PC chair for WSDM'11 in HongKong, WebSci'12 in Evanston, US, CIKM'13 in San Francisco, and for the WWW'13 Social networks and Graph Analysis Track in Rio De Janeiro.

Contact Info: Matteo Lissandrini (