Hello,

We have been reading the fenced frame ads reporting page for a while and issues #289 (for the beacon) and #281 (for the double join). We wanted to check with you if our understanding of how we could use ARA within this framework is correct. Here is a sequence diagram which explains how a unique id, called here EventId, generated during a contextual request by the SSP, could be be transferred to the reporting worklet and therein to the AdBeacon, and eventually used to uniquely identify the click on a Fenced Frame ad and be joined with the contextual information gathered during at the contextual request. We took the specific example of registerAdBeacon which was newly added to the Fenced Frame Ads Reporting page, but it should be very similar when tracking clicks using reportEvent.

Thanks a lot!

Addendum:
Code for generating this diagram on https://sequencediagram.org/, feel free to use it and modify it if needed.

title EventId propagation

participant FF
participant AdBeacon
participant Reporting Worklet
participant Bidding Worklet
participant Browser
participant SSP
participant DSP

SSP->DSP:contextual bid request
activate DSP
DSP -> SSP:Contextual response\n(includes EventId)
Bidding Worklet<-SSP:perBuyerSignal (includes EventId)
abox over Bidding Worklet:RunAdAuction
Reporting Worklet<-Bidding Worklet:ReportWin(EventId)

Reporting Worklet->DSP:call done after reportWin(EventId)
AdBeacon<-Reporting Worklet:registerAdBeacon({\n'reserved.top_navigation':\nURL+EventId})
FF->AdBeacon:setReportEventData\nForAutomaticBeacons\n(FF event data)
note over FF:click then\nnavigation
AdBeacon->DSP:URL?event_id=EventId\nFF event data in the body\nheader: attribution-reporting-eligible
Browser<--DSP:Attribution-Reporting-Register-...
deactivate DSP