1. A method comprising: filtering, by one or more computer processors, a plurality of resource candidates based on a first filter of a first filter chain to yield a first set of filtered resource candidates, the first filter chain comprising a first set of serially connected filters; determining, by the one or more computer processors, that the first filter of the first filter chain includes a reference to a second filter chain, the second filter chain comprising a second set of serially connected filters, different than the first set of serially connected filters; and after filtering the plurality of resource candidates based on the first filter of the first filter chain, filtering, by the one or more computer processors, the first set of filtered resource candidates based on each filter in the second filter chain to yield a second set of filtered resource candidate.