Foundations of Crowd Data Sourcing

Crowdsourcing techniques are very powerful when harnessed for the purpose of collecting and managing data. In order to provide sound scientific foundations for crowdsourcing and support the development of efficient crowdsourcing processes, adequate formal models must be defined. In particular, the models must formalize unique characteristics of crowd-based settings, such as the knowledge of the crowd and crowd-provided data; the interaction with crowd members; the inherent inaccuracies and disagreements in crowd answers; and evaluation metrics that capture the cost and effort of the crowd. In this paper, we review the foundational challenges in modeling crowd-based data sourcing, for its two main tasks, namely, harvesting data and processing it with the help of the crowd. For each of the two task types, we dive into the details of one foundational line of work, analyzing its model and reviewing the theoretical results established using this model, such as complexity bounds and efficient algorithms. We also overview a broader spectrum of work on crowd data sourcing, and highlight directions for further research.