Introduction to IR

This lecture provides an introduction to Information Retrieval (IR), the technology underpinning web search engines and many modern AI systems. We will cover the key concepts of relevance, indexing, and ranking, together with the main components of a standard IR system, including tokenisation, stemming, stopword removal, inverted indexes, and term weighting. The lecture will also discuss retrieval models and their evolution from classical lexical approaches to neural retrieval, before concluding with the increasingly central role of IR in modern AI systems, including answer generation with Retrieval-Augmented Generation (RAG).