Probability Ranking Principle
The fundamental goal of relevance ranking is often expressed in terms of the Probability Ranking Principle:
If an IR system's response to each query is a ranking of the documents
in the collection in order of decreasing probability of relevance, then
the overall effectiveness of the system to its users will be maximized.
- This serves as a guiding principle that underlies much research, but nevertheless overlooks such things as the size and scope of the document.
- The specificity of the document measures the degree to which its contents are focused on the information need. For example, the document might satisfy the need but also contain lots of other garbage.
- The exhaustivity of the document reflects the degree to which it covers the information related to the topic.
- The novelty of a document in a document list reflects how much new information the n-th search result gives to the user given the previous results.