attribution-reporting-api
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WICG
Marginal histograms?
Hi Charlie,
Thanks for clarifying #183. This leads me to a follow up question about adding support for "marginal histograms".
The number of non-negligible partitions ((adv, pub) pairs per time window) will easily be in the tens of thousands, potentially higher. There's also going to be a long tail of partitions with just a couple contributions, which sum to a significant fraction of all contributions.
Let's say I'd like to calculate some "global" aggregate, for example a "global spend" - would I have to add up the values from each partition? If so, the noise from each partition would accumulate in the final global aggregate, which is unfortunate.
I was wondering, would you say the query model could support "marginal histograms" as well? So that I could say "I'd like to query for key=12515, across all publishers and advertisers", or "I'd like to query for key=1414 for all publishers and advertiser=exampleadvertiser.com"? This would be very useful, if we could avoid the accumulated-noise problem.
Best regards, Jonasz
Looked into this and I think this should be OK privacy-wise as long as each histogram contribution is still only a function of each single (adv, pub) pair, and that contribution takes from the privacy budget of that pair which is the case in the current document.
This should be supported in the aggregation service. Please re-open if there's any further issues here.