What? How? Where? A survey of crowdsourcing

Crowdsourcing system recruits an undefined group of people to accomplish tasks proposed by a requester in a short time with low cost. Crowdsourcing makes great contributions in many fields. Building a crowdsourcing system faces many challenges, such as how to motivate people, how to decompose and assign tasks, how to control quality, how to aggregate contributions. In this paper, we explain what the crowdsourcing is and propose three necessary characters as criteria to judge a crowdsourcing system. Then, we introduce solutions to those challenges of crowdsourcing system. Finally, we talk about where crowdsourcing can be used and choose two fields to illustrate the usefulness of crowdsourcing. ? Springer Science+Business Media Dordrecht 2014.