Collaborative filtering is the process of filtering for information or patterns using techniques involving collaboration among multiple agents, viewpoints, data sources, etc. Applications of collaborative filtering typically involve very large data sets.
Were the women who were burned as witches during the Salem witch trials of 1692 really witches? Does a number exist that is greater than any number previously thought of? Is the future real? Are there real possibilities? And these questions aren't studied simply for a yes or no answer, but to determine in what sense these things exist if they do, and on what grounds we are able to say so.