Dipartimento di Ingegneria informatica, automatica e gestionale

Given an input of a set of objects each one represented as a vector of features in a feature space, the problem of finding the skyline is the problem of determining the subset of objects that are not dominated by any other input object. An example of an application is to find the best hotel(s) with respect to some features (location, price, cleanliness, etc.) The use of the crowd for solving this problem is useful when a score of items according to their features is not available. Yet the crowd can give inconsistent answers. In this paper we study the computation of the skyline when the comparisons between objects are performed by humans. We model the problem using the threshold model [Ajtai et al, TALG 2015] in which the comparison of two objects may create errors/inconsistencies if the objects are close to each other. We provide algorithms for the problem and we analyze the required number of human comparisons and lower bounds. We also evaluate the effectiveness and efficiency of our algorithms using synthetic and real-world data.