Algorithmics Group
Prof. Dr. Ulrik Brandes

	University	Department	Algorithmics
	Members	Research	Teaching	Software

• Members
• Research
  • Adaptive Layout
  • Clustering
  • NEXUS 1492
  • CARIB
  • Event Networks
  • Social Network Algorithmics
  • visone
  • Visual Navigation
  • Network Models
  • CLIQUE
  • Innovation Networks
  • Stress and Conflict
  • Data Quality
  • COSIN
  • GraphML
• Teaching
• Software

Research

Adaptive Network Layout (2015-2019)

DFG-funded project as part of SFB/TRR 161 Quantitative Methods for Visual Computing.

We plan to extend stress-minimization approaches for general graph layout. Adaptive algorithms shall be developed from quantitative descriptions of the effects of graph characteristics on layout features. Since extensive algorithmic experimentation will be required to understand empirically the response curves of such algorithms, we will also contribute to methodology in experimental algorithmics.

Skeleton-Based Clustering in Big and Streaming Social Networks (2014-2017)

DFG-funded project in collaboration with the group of Dorothea Wagner (KIT) as part of the Priority Program Algorithms for Big Data.

We intend to devise novel methods to cluster large-scale static and dynamic online social networks. Our approach is based on skeleton structures that represent and amplify variation in local cohesion, and that are defined locally to facilitate efficient computation. In addition to simplifying the clustering problem, they shall also provide a novel understanding of community dynamics, capturing more directly the agency of social actors.

NEXUS 1492: New World Encounters in a Globalizing World (2013-2016)

This is an ERC Synergy Project with Corinne L. Hofman (Archaeology, Universiteit Leiden) and Gareth R. Davies (Geochemistry, Vrije Universiteit Amsterdam).

The ambition of NEXUS 1492 is to rewrite a chapter in global history by focusing on transformations of indigenous, Amerindian cultures and societies across the historical divide of 1492. It investigates the impacts of colonial encounters in the Caribbean, the nexus of the first interactions between the New and the Old World. The project is a joint effort with groups from Universiteit Leiden and Vrije Universiteit Amsterdam.

Our role is the reconstructing of archaeological aetworks and their transformations. We address the transformations of archaeological networks of people, objects and ideas across the historical divide by foundational research on ways of reconstructing archaeological networks from sparse, fragmented and dissimilar datasets, driven by and tested in case-studies of interdependent, multi-level Amerindian networks in the period AD 1000-1800. Unparalleled by conventional methods, network approaches bring to archaeology the potential to model relations between past cultures, communities and individuals as opposed to emphasising the inherent qualities of such entities.

CARIB: Caribbean Encounters (2013-2016)

Joint Research Project with Corinne L. Hofman (Universiteit Leiden) and Patrick Degryse (KU Leuven). Our part is funded by BMBF via participation in ESF-HERA (Humanities in the European Research Area).

The cultural encounters between the Old and New Worlds are among the most infamous in human history. The Caribbean was the centre stage for interactions between cultures of dramatically different backgrounds, which after a turbulent colonial period eventually laid the foundations for the modern-day, multi-ethnic societies of the region. The universities of Leiden, Leuven, and Konstanz will combine archaeology, history, archaeometry, and network science to study the transformations of Amerindian culture and society as a result of these encounters. Through collaborations with local experts, the involvement of local communities, and the organisation of workshops and museum exhibitions, this project contributes to capacity building and historical awareness. In a geopolitically diverse islandscape, with an archaeological record that is under threat from natural disasters and the growing tourism industry, this project stimulates the valorisation of Caribbean cultural heritage.

Event Network Models of Social Interaction (2012)

A Google Research Award.

Tool-supported social interaction generates massive streams of relational event data. As proxies of user activity such data are assumed to be helpful in understanding and predicting, for instance, the popularity of artifacts (videos, documents, messages, etc.) and the behavior of individuals (activity bursts, churn, influence, etc.). We plan to combine methods from time-to-event analysis and network modeling into an approach that capitalizes on the inherently complex dependency structures in such data.

Social Network Algorithmics (2010-2016)

This is a Reinhart Koselleck Project funded by DFG.

We are exploring whether a genuinely algorithmic approach can serve to finally bridge the theory gap in social network analysis. While there is considerable doubt that it can even exist, a coherent methodological basis would constitute a major breakthrough for the rising network paradigm. Algorithmic research is used to systematically identify hidden theoretical assumptions and consequences of current methodology, and thus develop more deeply rooted foundations for empirical social network analysis.

visone (2002-2008, continuing)

visone is a collaborative effort with the group of Dorothea Wagner at Karlsruhe Institute of Technology (KIT). It is a DFG-funded project within the Priority Program Algorithmics of Large and Complex Networks.

The goal of visone is to develop models and algorithms to integrate and advance the analysis and visualization of social networks. An important aspect of visone is the design and implementation of a software tool intended for research and teaching in social network analysis. It is specifically designed to allow experts and novices alike to apply innovative and advanced visual methods with ease and accuracy.

Visual Navigation (2006-2010)

This is a joint project with Steffen Bogen, Felix Thürlemann (arts), and Albert Kümmel (media), all from the University of Konstanz, and in cooperation with Ruedi Baur and David Skopec (design) from HGKZ Zürich. The project is funded by VolkswagenStiftung within the programme Key Issues in the Humanities.

The focus of this project is on visual navigation using schematic maps. Its aim is to explore the long tradition of this cultural technique as a space of options for the assessment and improvement of systems in use today. We can draw on historic examples of schematization, but may also discover their historic alterity. The project challenges the arthistorical interpretation of examplary visual objects and the development of basic concepts of picture theory and media science. A diagrammatic perspective on schematic maps allows for the application of semiotic concepts based on the bipolar notions of icon and index. The much-cited iconic turn is thereby given a new, action-oriented, meaning.

Graphical Support for Network Evolution Models (2006-2012)

This project is part of the ECRP Dynamics of actors and networks across levels: individuals, groups, organizations, and social settings (coordinated by T.A.B. Snijders, Oxford/Groningen) with participating groups from The Netherlands, France, United Kingdom, Spain, Sweden, and Switzerland.

The aim of this project is to develop and employ network visualization methods for the interpretation and model diagnosis of statistical models for social network evolution. The models of Snijders et al., which form the basis of our ECRP proposal, are rather algebraic and require complementary graphical methods to be utilized more easily. These methods will be developed in a feedback-loop with both the core modeling project and our substantively and empirically oriented partner projects.

CLIQUE (2009-2013)

Clique is a Science Foundation Ireland funded (SFI) Strategic Research Cluster focusing on network analysis and visualization. It is a joint initiative of University College Dublin and DERI and NUI Galway with industry partners IBM, Idiro Technologies and Norkom Technologies. We are external collaborators contributing in particular to the network visualization workpackage.

Clique addresses four of the core research challenges in network analysis and visualization. These are the identification of coherent communities, the identification of nodes that have pivotal roles, the identification of network structure that is remarkable or anomalous and the question of how to model and analyze information flow. In particular the research will address datasets that are massive, multi-attribute and dynamic.

Public Policy Value of Open Innovation Networks (2007-2010)

This joint project with Patrick Kenis from the Department of Organisation Studies at Tilburg University is funded by NWO (Nederlands Organisatie for Wetenschappelijk Onderzoek) within the programme Netwerken van Netwerken.

Open innovation involves the loosely regulated collaboration of different actors, leading to the creation or modification of both tangible and intangible goods and services. We believe that understanding the structure of open innovation networks, seen as a special case of ICT-based networks, is of great potential value for policy making. Consequently, policy makers need to be able to assess the quality of such networks (for example in terms of the quality of information provided, their reliability, or neutrality) in order to decide whether to encourage, tolerate or restrict them. We hypothesize the architecture of these networks to be a good predictor of the qualit y of such networks. On the basis of theoretical analyses and the study of a number of purposefully selected cases of open innovation networks we intend to assess how the architecture of open innovation networks effects the quality of their output.

Social Stress and Conflict Resolution (2008-2010)

This research initiative aims at integrating the research activities of stress and conflict researchers working at the University of Konstanz. Building on significant disciplinary efforts in three departments, the research initiative will stimulate multi-disciplinary research on the interrelationship between escalated forms of conflict, the resulting social stress and attempts to resolve these conflicts.

The projects will contribute to the inter-linkage between individual and social causes and consequences of stress and conflictive behavior and analyze conflict resolution mechanisms that take these interdependencies into account. Such a multi-level perspective is particularly important in an area of research where purely disciplinary approaches often reach their limitations. The research initiative is initially based on six projects; on-going projects led by the Principal Investigators will be integrated into these activities.

Quantitative Methods and Survey Research (2008-2010)

This research initiative aims at improving the basis for working with process-generated data. Our sub-project focuses on inconsistencies in survey-collected network data.

COSIN (2002-2005)

COSIN was a research project funded by the European Commission in the 5th Framework Programme with participating research groups from France, Germany, Italy, Spain, and Switzerland.

The goal of COSIN is to develop theoretical methodologies for the characterization of complex networks, statistical models for network growth and evolution, and visualization tools for large-scale systems. The notion of complexity in this project rests on the assumption that quantitatively larger systems are qualitatively different.

GraphML (continuing)

GraphML is a comprehensive and easy-to-use file format for graphs. It consists of a language core to describe the structural properties of a graph and a flexible extension mechanism to add application-specific data.

Unlike many other file formats for graphs, GraphML does not use a custom syntax. Instead, it is based on XML and hence ideally suited as a common denominator for all kinds of services generating, archiving, or processing graphs.