The present invention contemplates a variety of engines, methods and systems for making computer-assisted choices among heterogeneous alternatives. More specifically, engines, methods, and systems for normalizing heterogeneous parameters for scoring proposals are contemplated. The present invention includes a comparison engine that generates a ranked list of alternatives such as proposals or items of consumer merchandise, in which each alternative is assigned a weighted score that reflects the importance of tradeoffs among various criteria. The comparison engine includes a tradeoff module that has tradeoff criteria having a range of possible values, a criteria behavior module capable of analyzing attributes, including values of the criteria, for a set of alternatives and generating a set of scores reflecting the desirability of the attributes using logic diagrams, and a scoring and ranking module that takes the assigned values from the tradeoff module and the set of scores from the criteria behavior module and generates a ranked list of alternatives. The comparison engine assesses and scores the proposals automatically, at the click of a button, without the need for a human to read, assess, and score the proposals. The comparison engine can be used to facilitate a reverse auction, in which suppliers submit bids to a purchaser who desires specific goods or services. The present invention also discloses a method for generating a ranked list of alternatives, including the steps of generating a homogeneous matrix of scores based on a heterogeneous matrix of attributes and alternatives, receiving a tradeoff value, and generating a ranked list of alternatives based on the homogeneous matrix of scores and the tradeoff value. The present invention further discloses a system for generating a ranked list of alternatives, including means for generating a homogeneous matrix of scores based on a heterogeneous matrix of attributes and alternatives, means for receiving a tradeoff value, and means for generating a ranked list of alternatives based on the homogeneous matrix of scores and the tradeoff value.