8. A system for corroborating facts, comprising: one or more processors; memory; and one or more programs stored in the memory, the one or more programs comprising instructions to: identifying a plurality of source documents including facts associated with a common subject; identify, from the plurality of source documents, one or more attribute-value pairs associated with the common subject; corroborate a fact, comprising a respective attribute-value pair of the one or more attribute-value pairs associated with the common subject, by determining that the respective attribute-value pair meets one or more predefined corroboration requirements; and in response to corroboration of the fact, updating a status of the respective attribute value pair in a fact repository; wherein the instructions to corroborate a fact includes instructions to: determine that a respective attribute of the respective attribute-value pair meets a first corroboration requirement; and determining that the respective attribute-value pair meets a second corroboration requirement.
10. The system of claim 8 , wherein the second corroboration requirement with respect to the respective attribute-value pair is based on a number of source documents having the respective attribute-value pair associated with the common subject.