Table of Contents
Current Topics in Information Access: IR Background
Last Time
Today
Some IR History
Information Retrieval
Structure of an IR System
PPT Slide
PPT Slide
PPT Slide
PPT Slide
Steps in a “typical IR System”
Stemming and Morphological Analysis
Automated Methods
Errors Generated by Porter Stemmer (Krovetz 93)
Query Languages
Simple query language: Boolean
Boolean Queries
Boolean Queries
Boolean Queries
Boolean Logic
Boolean Searching
Boolean Problems
Advantages and Disadvantage of the Boolean Model
Psuedo-Boolean Queries
Boolean Extensions
Ranking Algorithms
PPT Slide
Indexing and Representation: The Vector Space Model
Document Representation What values to use for terms
Document Vectors
Vector Representation
Document Vectors
Assigning Weights
Assigning Weights
tf x idf
tf x idf normalization
Vector Space Similarity Measure combine tf x idf into a similarity measure
Computing Similarity Scores
Documents in Vector Space
Computing a similarity score
Similarity Measures
Problems with Vector Space
Probabilistic Models
Probabilistic Retrieval
Probabilistic Models: Some Notation
Probabilistic Models: Logistic Regression
Probabilistic Models: Logistic Regression attributes
Probabilistic Models: Logistic Regression
Probabilistic Models
Vector and Probabilistic Models
Simple Presentation of Results
Problems with Vector Space
Evaluation
What to Evaluate?
What to Evaluate?
Relevance
Standard IR Evaluation
Precision/Recall Curves
Precision/Recall Curves
Precision/Recall Curves
Document Cutoff Levels
The E-Measure
TREC
Sample TREC queries (topics)
TREC
TREC Results
Blair and Maron 1985
Blair and Maron, cont.
Blair and Maron, cont.
PPT Slide
Creating a Keyword Index
Inverted files
Inverted Files
How Are Inverted Files Created
How Inverted Files are Created
How Inverted Files are Created
How Inverted Files are Created
An Example IR System
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