Aggregation Operators to Support Collective Reasoning

Moderation poses one of the main Internet challenges. Currently, many Internet platforms and virtual communities deal with it by intensive human labour, some big companies-such as YouTube or Facebook-hire people to do it, others-such as 4chan or fanscup-just ask volunteer users to get in charge of it. But in most cases the policies that they use to decide if some contents should be removed or if a user should be banned are not clear enough to users. And, in any case, typically users are not involved in their definition. Nobel laureate Elinor Ostrom concluded that societies-such as institutions that had to share scarce resources-that involve individuals in the definition of their rules performed better-resources lasted more or did not deplete-than those organisations whose norms where imposed externally. Democracy also relies on this same idea of considering peoples’ opinions. In this vein, we argue that participants in a virtual community will be more prone to behave correctly-and thus the community itself will be “healthier”-if they take part in the decisions about the norms of coexistence that rule the community. With this aim, we investigate a collective decision framework that: (1) structures (relate) arguments issued by different participants; (2) allows agents to express their opinions about arguments; and (3) aggregates opinions to synthesise a collective decision. More precisely, we investigate two aggregation operators that merge discrete and continuous opinions. Finally, we analyse the social choice properties that our discrete aggregator operator satisfies. © Springer International Publishing Switzerland 2016.Work funded by Spanish National project CollectiveWare code TIN2015-66863-C2-1-R (MINECO/FEDER).Peer Reviewe