Introduction to IR -- SALT86a (Another Look ...)

Introduction

• Boolean operators and queries
• Recall and Precision
• R and P Enhancement Devices: stemming, thesaurus, weighting

Blair & Maron Article

• Experiment: 40 queries, 40K documents (350K pages)
• Stairs
• P=.75, R=.20

Other Experiments

• Medlars, and failures
• indexing language
• document indexing
• search formulation
• user-system interaction
• NASA
• Cranfield

Overview of Automatic Methods

• Vector Weight: tf * idf
• Probabilistic Weight: log ( (N-n)/n )
• Term Discrimination
• Devices/transformations: phrase, thesaurus

Automatic Indexing Steps

• tokenize
• stop list
• stem
• weight
• find phrases
• build thesaurus