SEO (6) Search Engines

SEARCH ENGINES

Crawler based search engines

Search engines are software programs that provide users with URL of relevant internet web pages

relative to the keyword used to perform the search.

A crawler based search engine consists of:

1. Spider/Crawler visits a web page, stores a mirror image of all the information

gathered from the web page on visit date and time and follows URL to other web

pages within the site and other web sites. The mirror copy is called cached page.

The spider returns to all web pages previously crawled to maintain up to date information about these pages.

2. Indexer is a catalog which consists of copies of all web pages crawled by the spider

with date time stamp. There is generally a delay between spidering a web page and adding it to the index.

The search engine results are derived from the index and hence may not reflect the spidered web pages until the index is updated.

3. Search software searches through all pages recorded in the index in response to a query and returns URL of related

web pages ranked in an order determined by the search engine relevancy algorithm.

A relevant search engine result may be defined as the set of URLs displayed in response to a user query of which the user clicks one or more URLs.

Relevancy of search engine result is relative to the user as two users querying the same search engine with the exact same keyword may be searching for very different information.

source:SEARCH ENGINE OPTIMIZATION AND MARKETING by Binoy Varghese page 12-13

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