How Search Engines Operate?
Posted by admin - 28/07/09 at 02:07 amSearch engines have a short list of critical operations that allows them to provide relevant web results when searchers use their system to find information.
- Crawling the Web:
- Search engines run automated programs, called “bots” or “spiders” that use the hyperlink structure of the web to “crawl” the pages and documents.
- Estimates are that of the approximately 20 billion existing pages, search engines have crawled between 8 and 10 billion.
- When a user requested for information comes into the search engine the engine retrieves from its index all the documents that match the query.
- For example, a search for sports cars at Google returns approx. 6.25 million results, but a search for the same phrase in quotes (”sports cars“) returns only approx 245 thousand results. For more info other advanced operators go to http://www.google.com/support/websearch/bin/answer.py?hl=en&answer=136861
- Once the search engine has determined which results are a match for the query, the engine’s algorithm runs calculations on each of the results to determine which is most relevant to the given query.
- They sort these on the results pages in order from most relevant to least so that users can make a choice about which to select.
- Indexing Documents:
- Once a page has been crawled, its contents can be “indexed” – stored in a database of documents that makes up a search engine’s “index” and sort billions of documents can be completed in fractions of a second.
- Processing Queries:
- Ranking Results:
Major Search engines like Google, Yahoo! and MSN are among the most complex, processing computers in the world.
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