DAD is a comprehensive website ad management system. / DAD is a mod_perl application with advanced targeting capabilities, a comprehensive administrative interface, and automatic client reporting. Because it uses mod_perl, DAD can takes advantage of Apache API elements like subrequests and notes, and it can rely on persistent database connections through DBI. These features allow DAD to efficiently implement advanced targeting rules that would be impossible under CGI. / DAD can target ads by many factors, which include: remaining impressions, browser, domain name, number of times a user has seen an ad, virtualhost-specific environment variables, and other ads on a given page. The targeting code is written to allow easy addition of new targeting dimensions for site-specific needs. / DAD provides a web-based administrative interface for maintenance of ads and their targeting dimension, ad placement, and site and reporting parameters. Ad parameters and placement can be updated in real-time on a live site. Additionally, each advertiser can be given a password-protected URL where they can view automatically updated statistics about their ads. / To understand how DAD functions, it is necessary to understand how it organizes ads. Each ad belongs to one campaign and zero or more groups. Campaign is an advertiser-centric collection: all ads from a given advertiser will normally be in the same campaign. Group is a site-centric collection: all ads that could appear in a particular spot on the site will normally be in the same group. / When DAD is invoked from a page, it is passed a group name. The ad selected will generally be chosen from that group. Multiple invocations of DAD from the same page can request ads from the same or different group. /