1. A processor-implemented method of characterizing a target system, comprising: sending a query from a characterizing system, the query comprising an ontology of interest that describes and represents a domain of interest, a predicate, and a scoring algorithm, wherein the ontology of interest includes a plurality of nodes, each node of the plurality of nodes related to another node of the plurality of nodes, the predicate describing a membership qualification for a node in the ontology of interest; receiving a response comprising a score at the characterizing system, the score being generated with the scoring algorithm, the score representing an evaluation of the predicate to metadata associated with the target system and how well the metadata matches the ontology of interest; evaluating the score to characterize the target system, wherein the metadata of the target system is inaccessible to the characterizing system; and accepting that the metadata is inaccessible to a sender of the query.