BM25 and all that -- a look back

It is 30 years since the weighting-and-ranking function BM25 was published, and more than 55 years since I started work in the field we know as information retrieval.I will be talking about my experiences as an IR researcher over the period from 1968 to the early 2000s, including the development of the probabilistic model which led to BM25, and also some of the work on IR evaluation in the years since the Cranfield experiment.More generally, I will talk about some of the ways in which the field has changed and developed over that time, and about some of the characters who helped to shape the field, including my own interactions with them.