Hi,

I was wondering, has there been any discussion on how event-level Attribution Reporting API and FLEDGE fit together?

More specifically, I was wondering how navigational attribution sources (i.e. clicks) should be registered in FLEDGE.

1. To register a click, ARA explainer mentions that an attributionsrc parameter may be added to the anchor tag (see link).
2. FLEDGE ads will be subject to k-anonimity thresholds, and will be displayed in isolated Fenced Frames.

One implication of 1. + 2. is that the click-side data (source_event_id in ARA naming) will have a rather limited utility.

In my view, a more useful souce_event_id could be derived from perBuyerSignals (a "contextual source_event_id"):

• That would naturally fit the current design of reportWin and Fenced Frames Ads Reporting, which allow us to create a 'contextual event', and decorate it with information whether there was a click.
• With such a contextual source_event_id, we would also be able to attach coarse conversion information to the contextual event.

It seems that the problem is technical - we are unable to create the "contextual source_event_id", because FLEDGE forbids injecting any contextual information into the ad. If there was a way to tell the browser: "this is the contextual source_event_id for the ad, but make sure not to reveal it within the Fenced Frame", that would solve the problem.

Please treat this as a discussion starter, I'd be really curious if you have any thoughts on this.

// There is also the question of how aggregate ARA fits into FLEDGE, but I guess it's better to discuss it in a separate issue? It seems in the aggregate case the source registration could be based on more signals than just contextual.

Best regards,
Jonasz