1. Information Retrieval
First lessons

2. Basic ideas User needs information Information sources
Distinguish data, information, knowledge
Information sources
Very well organized, indexed, controlled
Totally unorganized, uncharacterized, uncontrolled
Something in between
Connect the two in a way that matches information needs to information available.

3. The role of databases Databases hold specific data items
Organization is explicit
Keys relate items to each other
Queries are constrained, but effective in retrieving the data that is there
Databases generally respond to specific queries with specific results
Browsing is difficult
Searching for items not anticipated by the designers can be difficult

4. The Web Extreme opposite of a database
No organization, no overall structure, no index or key to the content
Searching and browsing are supported, but generally are not complete. (You will not know if you got every good response to your request. You may be able to tell that you got the response that meets your need, but may not know if you got the best response available.)

5. Digital Library
Something in between the very structured database and the unstructured Web.
Content is controlled. Someone makes the entries. (Maybe a lot of people make the entries, but there are rules for admission.)
Searching and browsing are somewhat open, not controlled by fixed keys and anticipated queries.
Nature of the collection regulates indexing somewhat.

6. How do we know the response is good?
Precision
Of the results returned, what percentage are meaningful to the goal of the query?
Recall
Of the materials available that match the query, what percentage were returned?

7. Text: Retrieval process

8. The process sequence Query entered Results Ranked Query Interpreted
Index
searched
Items
retrieved

9. The collection Where does the collection come from?
How is the index created?
Those are important distinguishing characteristics
Inverted Index -- Ordered list of terms related to the collected materials. Each term has an associated pointer to the related material(s).

10. CITIDEL An example Digital Library
All items are relevant to computing education
Visit at
Part of the National Science Digital Library