The document discusses several key concepts related to formal semantics and information retrieval, including:
1) Formal semantics studies the meaning of natural language through theoretical approaches like compositionality and truth conditions. It helps machines process human language by understanding lexical relations and semantic scope.
2) Cranfield experiments in the late 1950s first identified differences between query language used by searchers and document language, inventing the concept of a "search language" to bridge this gap.
3) Lexical semantics analyzes relationships between words like synonyms, antonyms and semantic networks to help search engines understand query semantics rather than just document content.