1. Structure of IR Systems
INST 734
Module 1
Doug Oard 1

2. Segments The nature of Information Retrieval (IR) What IR systems do
The structure of interactive IR systems 2

3. Taylor’s Model of Question Formation
Q Visceral Need
End-user Search
Q Conscious Need
Intermediated Search
Q Formalized Need
Q Compromised Need
(Query)

4. Iterative Search Searchers often don’t clearly understand
The problem they are trying to solve
What information is needed to solve the problem
How to ask for that information
The query results from a clarification process
Dervin’s “sense making”:
Need
Gap
Bridge 8

5. Design Strategies Foster human-machine synergy Divide-and-conquer
Exploit complementary strengths
Accommodate shared weaknesses
Divide-and-conquer
Divide task into stages with well-defined interfaces
Continue dividing until problems are easily solved
Co-design related components
Iterative process of joint optimization 16

6. Human-Machine Synergy
Machines are good at:
Doing simple things accurately and quickly
Scaling to larger collections in sublinear time
People are better at:
Accurately recognizing what they are looking for
Evaluating intangibles such as “quality”
Both are pretty bad at:
Mapping consistently between words and concepts 17

7. Divide and Conquer Strategy: use encapsulation to limit complexity
Approach:
Define interfaces (input and output) for each component
Define the functions performed by each component
Build each component (in isolation)
See how well each component works
Then redefine interfaces to exploit strengths / cover weakness
See how well it all works together
Then refine the design to account for unanticipated interactions
Result: a hierarchical decomposition
Okay, I’ve presented a very complex field… how do we actually go about studying it?
Example of a decomposition that doesn’t make sense: separating engine from transmission 19

8. Supporting the Search Process
Predict
Source
Selection
Nominate
Choose
Query
Formulation
IR System
Source
Reselection
Search
Query
Query Reformulation
and
Relevance Feedback
Selection
Ranked List
Examination
Document
Delivery
Document

9. Supporting the Search Process
Source
Selection
Query
Formulation
IR System
Search
Query
Selection
Ranked List
Indexing
Index
Examination
Document
Acquisition
Collection
Delivery
Document

10. Process/System Co-Design

11. Looking Ahead Modules 2: Indexing Module 3: Ranking
Module 4: Interaction
Module 5: Evaluation