Generally, a fact witness may only testify based on personal knowledge. Nevertheless, the Federal Rules of Civil Procedure allow corporations to appoint a representative to testify on their behalf, based on the corporation’s records and collective knowledge. Stephen M. Harnik and Armin Kaiser have co-written an article which analyzes how such testimony can - and cannot - be used at trial.
The Article can be downloaded here. 
 Originally published in volume 24, number 1 of the NYSBA NY Litigator Spring 2019, a publication of the Commercial & Federal Litigation Section of the New York State Bar Association.