1. A computer-implemented method, comprising: selecting, by a data processing device, a first contextual profile for a first resource, the first contextual profile specifying topic values that represent measures of relevance of the first resource for each of a plurality of topics; identifying a second resource that is identified as relevant to the first resource; computing a second contextual profile for the second resource based on a function of the first contextual profile; and providing the second contextual profile to a processing system that is configured to identify the second resource as relevant to at least one topic when at least one topic value in the second contextual profile satisfies a topic value threshold.