I have been working on exchange as an architect since its original inception. One of my tasks was to build the domain APIs for the sales domain. The original 3 categories we picked were for merchandisable vehicles, quoting and payments. We thought that these were a great start in enabling the end to end commerce that the Exchange was originally conceived for. I worked with a number of industry experts to help build the requirement and with other Exchange architects to ensure we had consistency between our APIs that would give us a great developer experience.