Abstract: The invention described herein provides a method, apparatus, and software for implementing a unified trading structure for use in a computerized trading system that implements trading relationship mechanisms for participant roles, including: selecting a set of characteristics which are common to a plurality of trading relationship mechanisms; the characteristics including: identifying participants for each participant role, terms and conditions that apply to all or selected participants, a description of the relationship, storing the characteristics. Preferably the method may include at least one attachment, which is stored, storing the characteristics, and the at least one attachment. The characteristics of the attachment may include Uniform Resource Information: mime type; and optional content.