This paper describes MARI (Multi-Attribute Resource Intermediary), a project which proposes to improve online marketplaces, specifically those that involve the buying and selling of non-tangible goods and services. MARI is an intermediary architecture intended as a generalized platform for the specification and brokering of heterogeneous goods and services. MARI makes it possible for both buyers and sellers alike to more holistically and comprehensively specify relative preferences for the transaction partner, as well as for the attributes of the product in question, making price just one of a multitude of possible factors influencing the decision to trade. Ultimately, we expect that the ability to make such specifications will result in a more efficient, richer, and integrative transaction experience.