1. A computer-implemented method for corroborating facts, comprising: at a computer system including one or more processors and memory storing one or more programs, the one or more processors executing the one or more programs to perform the operations of: identifying a plurality of source documents including facts associated with a common subject; identifying, from the plurality of source documents, one or more attribute-value pairs associated with the common subject; corroborating 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 corroborating the fact includes: determining 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.