The technology behind search is much older than you might imagine. Philip Bagley described the basic processes behind search in his 1951 Master’s thesis based on the functionality of the MIT Whirlwind computer. IBM developed the inverted index file structure still in use in most enterprise search applications in around 1975. The initial development of the BM25 ranking model by Stephen Robertson and Karen Sparck-Jones started at roughly the same time, yet BM25 (link to a very good video that explains ranking models) remains an important component of most text-retrieval software.
