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A Search-based Method for Forecasting Ad Impression in Contextual Advertising. Defense. Overview. Background: Web and contextual advertising Motivation: importance of volume forecasting in contextual advertising Methodology: forecasting volume as an inverse of the ad retrieval Experiments.
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A Search-based Method forForecasting Ad Impression in Contextual Advertising Defense
Overview • Background: Web and contextual advertising • Motivation: importance of volume forecasting in contextual advertising • Methodology: forecasting volume as an inverse of the ad retrieval • Experiments
Web Advertising • Huge impact on the Web and beyond • $21 billion industry • Main textual advertising channels: • Search advertising • Contextual advertising
CA Basics • Supports a variety of the web ecosystem • Selects ads based on the “context”: • Web page where the ads are placed • Users that are viewing this page • Interplay of three participants: • Publisher • Advertiser • Ad network • Advertiser’s goal is to obtain web traffic
Importance of ImpressionVolume • Critical in planning and budgeting advertising campaigns • Common questions for advertisers and intermediaries: • Bid value • Impact of ad variations • Timing of the campaign
A Challenging Problem of Impression forecasting • CA platforms are complex systems • Have hundreds of contributing features • A moving target, dynamic • Publisher‘s content and traffic vary over time • Large scale computation: billions of page views, hundreds of millions of distinct pages, and hundreds of millions of ads • Dynamic bid landscape • Competitors and what they are willing to pay
Current practice • Run test ad in real traffic for a few days • Simultaneously with the baseline • Compare with the baseline • Obvious drawbacks: • Use ad serving infrastructure • Expensive • Inefficient • Very long turn-around time
Forecasting as Inverse of AdRetrieval • Ad retrieval: given a page and a set of ads find the best ads • Forecasting: given an ad and a set of past impressions, find where the ad would have been shown if it were in the system • This work: assumes ads selected based on similarity of features: • Use the WAND (Broder et al, CIKM 2003) DAAT algorithm as page selection • Similarity of ad and context feature vectors: requires monotonic scoring function – this work uses dot product • Features can be based on either user of page context.
Conceptual Work Flow • Keep all the data used in ad retrieval for a given period • For an unseen/incoming ad: • Examine each impression • Score the ad using the ad retrieval algorithm • Compare the ad score with the score of the lowest ranking ad shown in the page view • Count the impressions where the ad would have been shown
Main challenge: scale • In order to beat scalability problem: • Index only unique pages • Adaptation of the WAND algorithm for count aggregation needed in forecasting • A Two-level Process • Use a posting list order to allow early termination
Indexing Unique Pages • The revenue estimate of an ad-page pair: score(p,a) = similarity(p,a)*bid • Revenue estimate for the lowest ranking ad: minScorep • For repeating pages the similarity is constant • However, ads and bids vary: • Could change the lowest ranking ad of a unique page • Only one index entry per unique page: What revenue to store for the lowest ranking ads? • Save a distribution of estimates {rev1…revn} • Assign median to the minScorep • MinScorep is recomputed based on the current ad supply
Two-level process (Impression forecasting) • First phase (approximate) evaluation: • maxWeightf = max{wf,p : for all p} • Full evaluation:
Framework • Offline processing • Analyzing the pages • Building a page inverted index • Creating a page statistics file • Online processing • We use the inverted page index and page statistics to forecast the # of impressions of a given ad. • Output • Given a ad and bid, output the # of imp • Give a ad, output the curve describe the relation b/w bid and # of impressions
Experiment Results • Day to day forecast • Week to week forecast
Observations: • Similar results between day-day and week-week forecasting. • The errors seems big, however, • Due to the traffic fluctuation. • Even with large margin of error, our result is still significant (it’s the best of its kind, and it’s still acceptable in campaigning budgeting and advertising strategy)
Top row has a good prediction. • Bottom row does not match well due to traffic fluctuation, but match the trend and sharp very well.
Tradeoff b/w efficiency and accuracy • Changing the value of minScorep will have effect on the output of the first level
Ad Variation Example • Subtle difference could lead to dramatic performance change
Conclusion • Ad retrieval algorithm is the determining factor in the CA impression volume forecasting • Introduced a search-based forecasting as inverse of ad retrieval • Promising experimental results • Further work: combine search with learning approaches to further improve forecasting.