“…However, in evaluating queries in community based systems, a major issue is to assess the quality and veracity of the answers, by estimating the trust of both the information sources and the responders, and by ascertaining their expertise. Model-based FQASs based on multi-criteria decision making and aggregation operators can be a potential promising approach [113,114]. Another issue in such contexts is estimating the answers validity that varies in time and space, meaning that the systems have to put an emphasis on the temporal and spatial dimensions.…”