02.06.2023

Four Papers accepted at IJCAI

We are proud to announce that four papers by our group members were accepted at the International Joint Conference on Artificial Intelligence (IJCAI) on 19-25 August in Macao, China. The acceptance rate of the conference was only about 15%. The following paragraphs describe the results of the four papers.

Real-world networks have many interesting properties. For example, the network might exhibit a dynamic nature, where changes are happening in its structure over time, and at the same time, those changes are not governed by a central authority, but by multiple people where each one of them follows their own interest. These dynamic changes can be modelled with temporal graphs and the selfish agents can be modelled with network creation games. In the paperTemporal Network Creation Games, the authors combine these two established concepts to create a model accurately captures the aforementioned properties of real-world networks. They analyze basic properties of the model such as hardness of computing the best agents strategy, and the quality of the constructed graphs.

The second paper Strategic Resource Selection with Homophilic Agents deals with the strategic selection of resources by selfish agents. Instead of the normal resource selection setting, the agents are heterogenous and their utility depends on the fraction of same-type agents using the resource. The authors show the existence and polynomial-time computability of equilibria and give bounds on the Price of Anarchy and Stability under some natural assumptions. This paper is based on the master thesis of Jonathan Gadea Harder who recently also joined our group as a PhD student.

In the modern world, information is becoming increasingly valuable and a big part of an employee's day in a company is spent exchanging information via meetings. Unfortunately, a lot of employees are reporting that they are becoming more and more unproductive due to spending time on meetings that are not really relevant to them. The goal of the paper Minimizing Reachability Times on Temporal Graphs via Shifting Labels is to examine how networks of information can be reconfigured such that the important information that needs to be disseminated into the network is spread as fast as possible with minimal number of changes to the schedule. The authors model such a network via temporal graphs where information between the nodes can only be exhanged in specific times steps. They show that such optimizations are generally computationally hard unless we study restricted classes of graphs or we bound some of the parameters of the network.

The last paper Continuous Schelling Games is based on the bachelor thesis of Jonas Schmidt and analyses population segregation caused by agents considering non-categorical attributes along a continuous scale, e.g. income, and extensively studies three natural models. The authors shed light on the existence and computation of equilibria, provide bounds on the Price of Anarchy and Stability, and insightful simulation results comparing the models.

Clean Citation Style 005

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Gadea Harder, Jonathan; Krogmann, Simon; Lenzner, Pascal; Skopalik, Alexander Strategic Resource Selection with Homophilic AgentsInternational Joint Conference on Artificial Intelligence (IJCAI) 2023: 2701–2709

[ Abstract ] [ BibTeX ] [ URL ] [ DOI ] [ Download ]

@inproceedings{gadeaharder2023strategic,
  abstract = {The strategic selection of resources by selfish agents is a classic research direction, with Resource Selection Games and Congestion Games as prominent examples. In these games, agents select available resources and their utility then depends on the number of agents using the same resources. This implies that there is no distinction between the agents, i.e., they are anonymous. We depart from this very general setting by proposing Resource Selection Games with heterogeneous agents that strive for joint resource usage with similar agents. So, instead of the number of other users of a given resource, our model considers agents with different types and the decisive feature is the fraction of same-type agents among the users. More precisely, similarly to Schelling Games, there is a tolerance threshold \(\tau \in [0,1]\) which specifies the agents' desired minimum fraction of same-type agents on a resource. Agents strive to select resources where at least a \(\tau\)-fraction of those resources' users have the same type as themselves. For \(\tau=1\), our model generalizes Hedonic Diversity Games with a peak at \(1\). For our general model, we consider the existence and quality of equilibria and the complexity of maximizing social welfare. Additionally, we consider a bounded rationality model, where agents can only estimate the utility of a resource, since they only know the fraction of same-type agents on a given resource, but not the exact numbers. Thus, they cannot know the impact a strategy change would have on a target resource. Interestingly, we show that this type of bounded rationality yields favorable game-theoretic properties and specific equilibria closely approximate equilibria of the full knowledge setting.},
  author = {Gadea Harder, Jonathan and Krogmann, Simon and Lenzner, Pascal and Skopalik, Alexander},
  booktitle = {International Joint Conference on Artificial Intelligence (IJCAI)},
  keywords = {ijcai jonathangadeaharder pascallenzner simonkrogmann year2023},
  pages = {2701-2709},
  title = {Strategic Resource Selection with Homophilic Agents},
  year = 2023
}

Deligkas, Argyrios; Eiben, Eduard; Skretas, George Minimizing Reachability Times on Temporal Graphs via Shifting LabelsInternational Joint Conference on Artificial Intelligence (IJCAI) 2023: 5333–5340

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Bilò, Davide; Cohen, Sarel; Friedrich, Tobias; Gawendowicz, Hans; Klodt, Nicolas; Lenzner, Pascal; Skretas, George Temporal Network Creation GamesInternational Joint Conference on Artificial Intelligence (IJCAI) 2023: 2511–2519

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@inproceedings{bilo2023temporal,
  abstract = {Most networks are not static objects, but instead they change over time. This observation has sparked rigorous research on temporal graphs within the last years. In temporal graphs, we have a fixed set of nodes and the connections between them are only available at certain time steps. This gives rise to a plethora of algorithmic problems on such graphs, most prominently the problem of finding temporal spanners, i.e., the computation of subgraphs that guarantee all pairs reachability via temporal paths. To the best of our knowledge, only centralized approaches for the solution of this problem are known. However, many real-world networks are not shaped by a central designer but instead they emerge and evolve by the interaction of many strategic agents. This observation is the driving force of the recent intensive research on game-theoretic network formation models. In this work we bring together these two recent research directions: temporal graphs and game-theoretic network formation. As a first step into this new realm, we focus on a simplified setting where a complete temporal host graph is given and the agents, corresponding to its nodes, selfishly create incident edges to ensure that they can reach all other nodes via temporal paths in the created network. This yields temporal spanners as equilibria of our game. We prove results on the convergence to and the existence of equilibrium networks, on the complexity of finding best agent strategies, and on the quality of the equilibria. By taking these first important steps, we uncover challenging open problems that call for an in-depth exploration of the creation of temporal graphs by strategic agents.},
  author = {Bilò, Davide and Cohen, Sarel and Friedrich, Tobias and Gawendowicz, Hans and Klodt, Nicolas and Lenzner, Pascal and Skretas, George},
  booktitle = {International Joint Conference on Artificial Intelligence (IJCAI)},
  keywords = {georgeskretas hansgawendowicz ijcai nicolasklodt pascallenzner sarelcohen tobiasfriedrich year2023},
  pages = {2511&ndash;2519},
  title = {Temporal Network Creation Games},
  year = 2023
}

Bilò, Davide; Bilò, Vittorio; Döring, Michelle; Lenzner, Pascal; Molitor, Louise; Schmidt, Jonas Schelling Games with Continuous TypesInternational Joint Conference on Artificial Intelligence (IJCAI) 2023: 2520–2527

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