5. Conclusions and future research
In this paper we describe endorsement deduction, a preprocessing algorithm to enrich the endorsement digraphs of a social network with endorsements, such as LinkedIn or ResearchGate, which can then be used in connection with a ranking method, such as PageRank, to compute an authority score of network members with respect to some desired skill. Endorsement deduction makes use of the relationships among the different skills, given by an ontology in the form of a skill deduction matrix. A preliminary set of experiments shows that the rankings obtained by this method do not differ much from the rankings obtained by simple PageRank, and that this method represents an improvement over simple PageRank with respect to two additional criteria: number of ties, and robustness to collusion spam. Our experiments also show that the benefits provided by PageRank with deduction are likely to increase in the future, with the densification of the endorsement networks, and the introduction of new skills. However, this has to be confirmed by larger-scale experiments.