a presentation system accepts presentations or references to presentations from prospective presenters . some or all of the presentations or references are stored in a database and referenced by keywords such that presentations to be presented in response to particular searches can be identified . a presentation manager handles accepting bids and settling terms between prospective presenters . the results of such processes might be stored in a presentation details database . a presentation server handles retrieving presentations from the presentation details database for presentation to users along with requests such as search results . both the presentation manager and the presentation server can operate on a keywords - basis , wherein presentation terms specify keywords to be associated with particular presentations and the presentation server serves particular presentations based on keywords in a search query for which the presentations are to be returned . the association of keywords can be done using canonicalization so that , under certain conditions , different keywords are treated as the same keyword . canonicalizations might include plural / singular forms , gender forms , stem word forms , suffix forms , prefix forms , typographical error forms , word order , pattern ignoring , acronyms , stop word elimination , etc . conditions might include aspects of the search query state , such as the user &# 39 ; s demographics , the page from which the search query was initiated , etc .