Page 110 - DLIS405_INFORMATION_STORAGE_AND_RETRIEVAL

Unit 10: Information Storage and Retrieval System

Notes

Keyword searches that combine two or more terms imply a connection between
the terms. These connections are expressed in what is called Boolean terms or
operators. The three Boolean operators for keyword searching are AND, OR,
and NOT (or AND NOT).
Using AND and NOT will narrow search results; OR will expand the results. The sample thesis
above assumes an AND connection between terms: when you type in the search words, you’re
asking for all the documents with the words marijuana AND California AND legal in them. Many
databases and some search engines default into an AND search.
The sample search above could be broadened by using the OR option. If you used, for instance, the
words “legal OR lawful”, you would add another variable, a word meaning almost the same thing
as the word “legal”. Since this is a word search, the computer would now pick up articles that might
have the word “lawful” in place of “legal”.
Similarly, the NOT option changes the parameters of a search, cutting down on the number of
articles retrieved. The search “marijuana AND legal AND California NOT San Francisco” would
omit articles that mentioned San Francisco when discussing, for example, legal use of marijuana in
California.
Try to keep your search to only 3 to 4 relevant terms at a time, with their proper Boolean connections.
If you need to use more terms, try breaking your unwieldy single search into two or more smaller
searches.

10.7 Summary

• An information storage and retrieval system (ISRS) is a network with a built-in user interface
that facilitates the creation, searching, and modification of stored data.
• An ISRS is typically a peer-to-peer ( P2P ) network operated and maintained by private indi-
viduals or independent organizations.
• A significant difference between an ISRS and a database management system (DBMS ) is the
fact that an ISRS is intended for general public use, while a DBMS is likely to be proprietary,
with access privileges restricted to authorized entities.
• An information retrieval process begins when a user enters a query into the system.
• Precision and recall are two widely used metrics for evaluating the correctness of a pattern
recognition algorithm.
• Precision can be seen as a measure of exactness or fidelity, whereas recall is a measure of
completeness.
• In the field of information retrieval, precision is the fraction of retrieved documents that are
relevant to the search.
• Recall in information retrieval is the fraction of the documents that are relevant to the query
that are successfully retrieved.
• Precision and recall are the basic measures used in evaluating search strategies.
• In information science and information retrieval, relevance denotes how well a retrieved docu-
ment or set of documents meets the information need of the user.
• Effective searching in web-based databases depends on how well your search is formulated.

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