Talks

Here are few talks I've given, the slides may not be up to date! If you have any questions, do contact me.

Equity of Resources for Participatory Budgeting
2022 SSCW Meeting - June 23, 2022

We introduce a new family of normative principles for fairness in participatory budgeting. These principles are based on the fundamental idea that budget allocations should be fair in terms of the effort invested into meeting the wishes of each voter. This is in contrast to earlier proposals that instead are based on specific assumptions about the satisfaction voters with a given budget allocation. We analyse these new principles in axiomatic, algorithmic, and experimental terms.

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Fair Position Assignment
2022 SSCW Meeting - Computational and Topological Social Choice Workshop - June 22, 2022

We study a model for fair division in which agents, aside from getting allocated a bundle of items (that can include both goods and chores), are also to be assigned a position on a social graph. We focus on the local variant of natural fairness criteria: local envy-freeness, local envy-freeness up to one item and local proportionality. For each criterion, we study the computational complexity of the task of producing a fair position assignment and, possibly also an item allocation. Specifically, we focus on how different graph topologies influence the complexity of these problems. In many cases both tasks prove to be intractable for the criteria that we consider. Then, we consider the parameterized complexity of the problem. We show how the problem is equivalent to the known dichotomy conjecture for the parameterized graph embedding problem. Thus, we focus on tree-like graphs, and prove fixed-parameter tractability for all criteria but local proportionality, using a set of parameters that are, under some assumptions, reasonably small.

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Mechanism Design for Participatory Budgeting
AAMAS 2022 - Doctoral Consortium - May 8, 2022

When seeking for suitable mechanisms for participatory budgeting, one has to decide on which criteria to assess them. In this talk, I briefly present several appealing criteria for PB mechanisms. I introduce each of them and discuss their impact on the design of PB mechanisms.

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Effort-Based Fairness for Participatory Budgeting
Oberseminar Düsselorf Computational Social Choice Group - March 30, 2022

In this talk I present a recent work with Jan Maly, Ulle Endriss and Martin Lackner. We introduce a new family of normative principles for fairness in participatory budgeting. These principles are based on the fundamental idea that budget allocations should be fair in terms of the effort invested into meeting the wishes of each voter. This is in contrast to earlier proposals that instead are based on specific assumptions about the satisfaction voters with a given budget allocation. We analyse these new principles in axiomatic and algorithmic terms.

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Non-Standard Models for Participatory Budgeting
Workshop Celebrating Sirin Botan's Defense - Nov. 25, 2021

In this talk I will discuss several recent papers on the topic of participatory budgeting. Participatory budgeting is usually studied as an extension of multi-winner voting, where selecting a candidate results in paying a cost, and where a budget limit constrains the cost of the selected candidates. Although highly relevant for the technical analysis, this approach does not fully capture participatory budgeting processes as they happen in real life. This talk aims at presenting other models for participatory budgeting that more closely resemble these real-life processes. We will discuss the idea of a two-stage model where agents first propose some projects and then vote over the shortlisted projects. We will also have a look at what changes when the process is repeated over several years. Finally, we will have a look at how to include additional constraints on top of the budget limit: quotas over categories of projects, dependencies between the projects, ...

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Mechanism Design for Participatory Budgeting
ADT 2021 - PhD Day - Oct. 5, 2021

When seeking for suitable mechanisms for participatory budgeting, one has to decide on which criteria to assess them. In this talk, I briefly present several appealing criteria for PB mechanisms. I introduce each of them and discuss their impact on the design of PB mechanisms.

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Improving the Buurtbudget: Can Mathematics and Computer Science Help?
Science Park Open Dag - Oct. 2, 2021

The buurtbudget, known as participatory budgeting in English, is a democratic process aiming at involving citizens in public spending decisions. In several neighborhoods of Amsterdam, residents already can vote for community-driven projects to be paid for from public funds. However, organizing this process is not straightforward, especially when it comes to making a decision based on the ballots that have been submitted. During this talk, we will see why some natural procedures to determine the winning projects suffer some drawbacks and how to circumvent those drawbacks.

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Designing Participatory Budgeting Mechanisms Grounded in Judgment Aggregation
8th International Workshop on Computational Social Choice - June 7, 2021

This talk presents the paper "Designing Participatory Budgeting Mechanisms Grounded in Judgment Aggregation" that was published at KR-2020. We prepared a lightened version for COMSOC-2021, focusing more on the COMSOC parts of this work (compared to the KR version).

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A Selective Literature Review of the Truth Tracking Approach in Computational Social Choice
Computational Social Choice Seminars - Nov. 26, 2020

In this talk I will give a general overview of the epistemic approach in computational social choice. In this body of literature, voting is seen as a mechanism to recover the objectively best outcome for the society, given noisy votes. I will discuss the general framework as well as some selected recent contributions, reviewing the main concepts used in the literature.

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Designing Participatory Budgeting Mechanisms Grounded in Judgment Aggregation
17th International Conference on Principles of Knowledge Representation and Reasoning - Sept. 18, 2020

We introduce a new approach for designing rules for participatory budgeting, the problem of deciding on the use of public funds based directly on the views expressed by the citizens concerned. The core idea is to embed instances of the participatory budgeting problem into judgment aggregation, a powerful general-purpose framework for modelling collective decision making. Taking advantage of the possibilities offered by judgment aggregation, we enrich the familiar setting of participatory budgeting with additional constraints, namely dependencies between projects and quotas regarding different types of projects. We analyse the rules obtained both in algorithmic and in axiomatic terms.

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A Review of the Computational Social Choice Literature on Participatory Budgeting
Computational Social Choice Seminars - Nov. 25, 2019

Participatory Budgeting is a growing topic in social choice. Introduced in the late 1980s in Brazil, it is now viewed as a critical topic to improve the democratic process. In this talk I introduced the concept of Participatory Budgeting and gave an overview of the related literature in the field of Computational Social Choice.

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Almost Group Envy-free Allocation of Indivisible Goods and Chores
Computational Social Choice Seminars - Nov. 5, 2019

In this talk I presented some recent work I have been doing with Haris Aziz. We consider a multiagent resource allocation setting in which an agent's utility may decrease or increase when an item is allocated. We present stronger and relaxed versions of the group envy-freeness concept that are especially suitable for the allocation of indivisible items. Of particular interest is a concept called group envy-freeness up to one item (GEF1). We studied which fairness concepts guarantee the existence of a fair allocation under which preference domain. For two natural classes of additive utilities, we designed polynomial-time algorithms to compute a GEF1 allocation.

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Credulous Acceptability, Poison Game and Modal Logic
SYSMICS 2019 - Jan. 22, 2019

This is a presentation of the work we did with Davide Grossi when I was visiting him in Groningen. It was presented during the Syntax Meets Semantics conference in Amsterdam. A paper was published at AAMAS 2019 on this work.

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