The role of the contracting officer for defining the evaluation criteria to be used during the source selection is best understood as "business adviser." The requiring activity/program office has the greatest interest in which supplier is selected for fulfilling its mission requirements, so the contracting officer should do his/her best to formalize the evaluation criteria (in accordance with the FAR/DFARS/agency regulations) to reflect what the using activity wants. Some users may consider "past performance" of a potential supplier more important for a particular acquisition than other users would for other acquisitions. Using activities are in the best position to determine the relative importance of past performance...when it is in fact required as an evaluation factor by regulation.