  Many important collective decision-making problems can be seen as multi-agent
versions of discrete optimisation problems. Participatory budgeting, for
instance, is the collective version of the knapsack problem; other examples
include collective scheduling, and collective spanning trees. Rather than
developing a specific model, as well as specific algorithmic techniques, for
each of these problems, we propose to represent and solve them in the unifying
framework of judgment aggregation with weighted issues. We provide a modular
definition of collective discrete optimisation (CDO) rules based on coupling a
set scoring function with an operator, and we show how they generalise several
existing procedures developed for specific CDO problems. We also give an
implementation based on integer linear programming (ILP) and test it on the
problem of collective spanning trees.
