Dear all,

Next week we are going to have two sessions of the Computational Social Choice Seminar at the ILLC. On Monday at 15:30 Simon will deliver an introductory tutorial on participatory budgeting. On Tuesday at 15:30 Zoi will talk about her recent work on the manipulation of positional scoring rules when voters report incomplete preferences.

I'm including both abstracts below.

As always, for more information on the COMSOC Seminar please consult http://www.illc.uva.nl/~ulle/seminar/.

All the best, Ulle

PS: Apologies for having forgotten to announce Jan Maly's talk to this mailing list. Jan will still be at the ILLC until the end of next week.

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Speaker: Simon Rey (ILLC) Title: A Review of the Computational Social Choice Literature on Participatory Budgeting Date and time: Monday 25 November 2019, 15:30 Location: F1.15, Science Park 107, Amsterdam

Abstract: 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 will introduce the concept of Participatory Budgeting and give an overview of the related literature in the field of Computational Social Choice.

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Speaker: Zoi Terzopoulou (ILLC) Title: Strategic Manipulation with Incomplete Preferences Date and time: Tuesday 26 November 2019, 15:30 Location: F3.20, Science Park 107, Amsterdam

Abstract: Many websites that recommend various services use crowdsourcing to collect reviews and rankings. These rankings, usually concerning a subset of all the offered alternatives, are then aggregated. Motivated by and generalising upon such scenarios, we axiomatise a family of positional scoring rules for profiles of possibly incomplete individual preferences. But many opportunities arise for the agents to manipulate the outcome in this setting. They may lie in order to obtain a better result by: (i) switching the order of a ranked pair of alternatives, (ii) omitting some of their truthful preferences, or (iii) reporting more preferences than the ones they truthfully hold. After formalising these new concepts, we characterise all positional scoring rules that are immune to manipulation. This talk is based on is joint work with Justin Kruger.

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