From fundamental concepts and results to recent advances in
computational social choice, this open access book provides a thorough
and in-depth look at multi-winner voting based on approval preferences.
The main focus is on axiomatic analysis, algorithmic results and several
applications that are relevant in artificial intelligence, computer
science and elections of any kind.
What is the best way to select a set of candidates for a shortlist, for
an executive committee, or for product recommendations? Multi-winner
voting is the process of selecting a fixed-size set of candidates based
on the preferences expressed by the voters. A wide variety of decision
processes in settings ranging from politics (parliamentary elections) to
the design of modern computer applications (collaborative filtering,
dynamic Q&A platforms, diversity in search results, etc.) share the
problem of identifying a representative subset of alternatives. The
study of multi-winner voting provides the principled analysis of this
task.
Approval-based committee voting rules (in short: ABC rules) are
multi-winner voting rules particularly suitable for practical use. Their
usability is founded on the straightforward form in which the voters can
express preferences: voters simply have to differentiate between
approved and disapproved candidates. Proposals for ABC rules are
numerous, some dating back to the late 19th century while others have
been introduced only very recently. This book explains and discusses
these rules, highlighting their individual strengths and weaknesses.
With the help of this book, the reader will be able to choose a suitable
ABC voting rule in a principled fashion, participate in, and be up to
date with the ongoing research on this topic.
