The 3 Rs of Search: Relevance, Recall, and Ranking

Relevance

Relevance is the prime directive of search: the guiding principle for a search engine is to return results that satisfy the searcher’s information need. That means understanding what the searcher wants and retrieving relevant results.

Recall

There’s more to search than precision. There’s also recall, the fraction of relevant results that are retrieved. Recall is about “the whole truth”, while precision is about “nothing but truth”.

Ranking

Finally, we get to ranking. Given the emphasis on the first page of results, search engine developers often prioritize investment in ranking. Ranking is indeed important enough to be the third R of search.

Summary

There you have it, the three Rs. Relevance, recall, and ranking are the ingredients for great search. There’s a fourth R that deserves mention: refinements. But that’s a subject for another post. In the meantime, I hope these three Rs provide a simple framework for thinking about search.

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