Relevance Ranking modules define the primitive search result ordering functions provided by the MDEX Engine. These primitive modules can be combined to compose more complex ordering behaviors called Relevance Ranking strategies.
You may also define and apply a strategy that consists of a single module, rather than a group of modules.
A Relevance Ranking strategy is essentially an ordered list of relevance ranking modules and (in a URL relevance ranking string) references to other relevance ranking strategies. The scores assigned by a strategy are composed from the scores assigned by its constituent modules. This composite score is constructed so that records are first ordered by the first module. After that, ties are broken by the subsequent modules in order. If any ties remain after all modules have run, the ties are resolved by the default sort. If after that any ties still remain, the order of records is determined by the system.
Relevance Ranking strategies are used in two main contexts in the MDEX Engine:
In Developer Studio, you apply Relevance Ranking to a search interface via the Search Interface editor and the Relevance Ranking Modules editor, both of which are documented in Developer Studio online help.
At the MDEX Engine query level, Relevance Ranking strategies can be selected to override the default specified for the selected search interface. This allows Relevance Ranking behavior to be fully customized on a per-query basis. For details, see the "URL query parameters for relevance ranking" topic.
