IAB Video Ad Serving Template (VAST)
The flow of the XML Wrapper method is very similar to the simplified diagram shown above with some important differences:
The Primary Ad Server or content management system is the first to receive a request.
The Primary Ad Server responds with a VAST XML document with a Wrapper ad including the impression URL, other tracking URLs, and click tracking URLs to be requested by the video player, along with the ad tag to the Secondary Ad Server from which the ad will be served.
The Video Player requests the ad tag from the Secondary Ad Server.
The Secondary Ad Server responds with the VAST document containing an InLine Ad, or alternatively can respond with a VAST document containing a second Wrapper Ad. Potentially there could be a third or fourth set of URLs as in the case where an ad network redirects to an agency ad server. This implies that the Video Player scripts need to keep track of multiple tracking URLs per event, per ad unit.
The Secondary Ad Server URLs are requested when certain events take place.
The Primary Ad Server URLs are requested when certain events take place. These URLs are determined by the first Wrapper Ad returned.
The Wrapper Ad includes a subset of descriptive and tracking elements from the InLine Ad, along with an extra element for the ad tag of the downstream ad server. Companion ads, Non-linear ads, and media delivery files are not supported in the Wrapper Ad.
VAST Ad Response
Sample XML documents and the standard XSD schema are available on the IAB website at www.iab.net/vast. See below for data definitions and explanatory notes.
Some key details of the XML response:
The top-level element in the VAST XML definition is the <ad>. An “Ad” contains some combination of video, companions, and non-linear units for a single advertiser.
A single VAST response may include multiple Ads from multiple advertisers. It will be up to the Video Player to determine the order, timing, placement, etc for the multiple ads. However, the sequential order of the Ad elements within a VAST response should be respected by the player.
The VAST response does not contain information on the placement or timing of the elements. It is up to the Video Player to determine the optimal inclusion points of the ads.
An Ad can either be of type InLine, meaning it contains all the elements necessary to display the visual experience, or of type Wrapper, which points to a downstream VAST document that must be requested from another server.
The XML response may indicate that no ads of any type are available. This would be indicated by the absence of any Ads.
An InLine Ad may include zero or one video elements. For example, if the Ad only includes a non-linear unit, there could be zero videos. In this case the required <impression> element of the Ad would refer to the non-linear asset and it is important that the non-linear element does not itself record an impression or else double-counting could occur.
An InLine Ad may include zero, one or more companion banners.
An InLine Ad may include zero, one or more non-linear elements.
The combination of the video ad, non-linear ads and companion ads is generally meant to represent a single ad
unit from a single advertiser.
© 2008 Interactive Advertising Bureau