A customizable ranking model of a search engine using custom ranking model configuration and parameters of a pre-defined human-readable format. The architecture can employ a markup language schema to represent the custom ranking model. In one implementation, the schema developed utilizes XML (extensible markup language) for representing the custom ranking model. Weights for dynamic and static relevance ingredients can be altered per ranking model and new relevance ingredients can be added. Additionally, features are provided for improving relevance such as adding terms to a thesaurus for synonym expansion, for example, the ability to deal with single terms either as compounds, and/or using custom word breaking rules.