Biomedical Engineering Reference
In-Depth Information
Searching and Information Theory
Information Theory forms the basis for our understanding of modern communications networks, and
provides a model for understanding the principles of search engines. Information Theory specifies the
amount of meaningful information that can be communicated from the Web server to the browser as
a function of the signal-to-noise level and the bandwidth of the medium. The greater the strength of
the desired signal compared to that of the noise—that is, the higher the signal-to-noise ratio—the
greater the amount of relevant data that can be propagated from the database through the Internet
to the user (see
Figure 4-8
).
Figure 4-8. Signal-to-Noise Ratio. Line height corresponds to the amount of
data available on a particular topic.
Figure 4-7
shows the application of Information Theory to search engine technology, where the
molecular biology database constitutes the information source, a Web server is the transmitter, the
Internet or other network serves as the medium, the search engine is the receiver, and the user's
Web browser or local application is the destination. Similarly, the relevant data in the database
constitutes the message to be transmitted, irrelevant data constitutes the noise source, and the
message presented to the user through a Web browser consists of both relevant and irrelevant data.
Figure 4-7. Searching and Information Theory. Following information
theory, both relevant and irrelevant data reach the user through the
Internet as a function of the search engine (receiver) and the relative
amounts of relevant and irrelevant data in the information source.
