19. A system comprising: a computer server comprising a processor and a database, the computer server configured to: access a plurality of content items authored by users of a social networking system; access a plurality of annotated events of time based broadcast media, the events having been aired during segments of time, the annotated events comprising metadata instances that have semantic information about the events; generate mappings between the content items and the annotated events, and between the content items and a plurality of topics; determine a first affinity score between a first population of the users who authored content items mapped to a first one of the events or a first one of the topics and a second population of the users who authored content items mapped to a second one of the events or a second one of the topics; determine a second affinity score between a third population of the users who authored content items mapped to a third one of the events or a third one of the topics and a fourth population of the users who authored content items mapped to a fourth one of the events or a fourth one of the topics; determine a third affinity score between the second population and the fourth population; and infer a fourth affinity score between the first population and third population based on the first, second, and third affinity scores.
21. The system of claim 19 , wherein the computer server is further configured to: access programming information regarding the events of time based broadcast media; and annotate the events using an alignment function to estimate the likelihood that the events are described by the metadata instances.