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How Do Search Engines Work?

How Do Search Engines Work? . Dr. Steve Broskoske Misericordia University. Do search engines actually search the entire Web when you enter search terms?. Yes and no. Yes , it does search the entire world. But not when you hit the search button. The search was already done in advance.

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How Do Search Engines Work?

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  1. How Do Search Engines Work? Dr. Steve Broskoske Misericordia University

  2. Do search engines actually search the entire Web when you enter search terms?

  3. Yes and no. Yes, it does search the entire world. But not when you hit the search button. The search was already done in advance.

  4. How do search engines actually work?

  5. Use the phone book! Analogy Without using a computer, how would you search out all of the people named Smith in the Wyoming Valley area?

  6. Search engines create an index, analogous to a phone book. When you search, you actually search the index! Word No. of Times URLtechnology 15 http://www.somewheretechnology 12 http://www.somewhereterabyte 4 http://www.somewhere

  7. Do search engines all produce the same qualityof results?

  8. Read more of Web page. Read all of Web page. Read part of Web page. No! The quality of results depends on the quality of the index. Indexes are not all the same! Also: Some indexes are arranged by humans, and others by computer algorithm.

  9. How do Web pages make it into a search engine?

  10. Web pages make it to a search engine through: • Web crawlers • Software that searches the Web and indexes Web pages. • Voluntary submission.

  11. Why can I sometimesnot find the wordsI searched for?

  12. Why you can’t find search terms on Web pages: • Web page content: • Has been changed. • Has been renamed or removed. Better search engines “cache” a copy of the page when they index it. The search terms were found on this page when this page was cached.

  13. Does any information hidefrom search engines? • There is much information that cannot be indexed by Web crawlers. This is know as the: • Dynamically generated Web pages. • Databases. • (Contents of PDF, PowerPoint, and Word documents used to be non-searchable.) Invisible Web Invisible Web Some search engines are designed to locate information on the invisible/deep Web.

  14. Review • Search engines read all of the Web pages in the world, and index them. • When you search, you are querying a search engine’s index. • Much of the Web is unsearchable (called the invisible Web). • Knowing how search engines work makes you a better searcher.

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