Clarification on seller use of IG

[patmmccann]

One of the primary problems with the https://github.com/WICG/turtledove proposal is the awkward position seller ATP are put in. SSPs, retailers, and big media sellers may know the content and audience quite well, but have no idea how to bid. PAAPI makes the IG owner the only entity that can bid. However, there are well-known issues with that eg WICG/turtledove#338 from a big retailer and this one WICG/turtledove#418 from the sandbox team. Proposals to solve this asymmetry with reporting or with delegation mechanisms, eg WICG/turtledove#399 (comment), are quite good but not available. In the meantime, sellers with knowledge of audience are asked to pivot into being buyers or to deeply trust one.

We're curious if this proposal allows a use case we're quite familiar with: supply platform sets an audience segment (or IG as we call them now) on one site, knows the content in-depth on another, and delivers the combination as a bid request deal id. PAAPI allows for onboarding and supply platform audience trafficking quite awkwardly, with entities having to morph far into unfamiliar territory. If this proposal didn't require such leaps, its barriers to adoption would be quite a bit lower than the experience so far in PA.