Information Technology Reference
In-Depth Information
computer packages) all rely upon detailed algorithms. In many
ways, algorithms are like recipes, offering the computer a list of
specific instructions that result in an application. Each application
utilizes a different algorithm. Similar Web programs by different
vendors may utilize different algorithms, or the algorithms may fol
low a similar approach but differ in their details. In rare cases,
algorithms may be identical. In many cases, details of algorithms
depend upon trade secrets, and companies are reluctant to disclose
those secrets publicly. Think about your local town or county fair
and its piebaking contest: Although anyone interested in apple pies
knows the basic ingredients and steps, you'll never know your Aunt
Linda's secret recipe that makes her pie win each year. In a similar
way, at a very detailed level, we often cannot know just how vari
ous applications work.
On the other hand, just like the basic recipe for an apple pie, ap
plications often follow common approaches for processing. We may
not know some specific details, but we may have a good idea of the
main elements of various algorithms. In this chapter, we consider
some of these general algorithms for several common Webbased
applications, such as search engines, Web advertising, and email.
In a typical interaction with a Web search engine, you en
ter one or more words into a text box. When you click
“submit”, your browser sends your query to the search
engine, the search engine idntifies Web pages which
match all of your words, and you receive the results of the
search as a listing in your browser.
To expand somewhat on this process, the work performed
by most search engines has these general characteristics.
1.
A search engine performs a search, based on a query given by
the user.
2.
The search engine maintains a database of Web pages.
3.
Information about Web pages often involves at least four ar
eas: category, description, title, and URL.
4.
Your query string is used to search the information areas for
the database of Web pages.
