Saturday, April 9, 2011

How Search Engine works ??

In last post I have explained about "what is SEO". Now we see how search engine works actually. If you want to become a SEO expert you should know how search engine works.

Working of Search Engines:
There 5 common processes follow by most of the search engines:

1. Crawling
2. Indexing
3. Query Processing
4. Data retrieving
5. Search Engine Ranking Pages(SERP) result

1. Crawling:

Web crawlers(also called as web robots or web spiders) are the programs which browses the links present on web. In order to browse the internet, they use the HTTP network protocol, which allows to talk to web servers and download or upload data from and to it. The crawler browses this URL and then seeks for hyperlinks (a tag in the HTML language). Then the crawler browses those links and moves on the same way. Basically they finds and retrieves pages on the web and hands them off to the indexer.

2. Indexing:

Web crawlers gives indexer the full text of the pages it finds. These pages are stored in index database. This index is sorted alphabetically by search term, with each index entry storing a list of documents in which the term appears and the location within the text where it occurs. This data structure allows rapid access to documents that contain user query terms.
Indexing of web content is a challenging task assuming an average of 1000 words per web page and billions of such pages. Indexes are used for searching by keywords; therefore, it has to be stored in the memory of computers to provide quick access to the search results.

3. Query Processing

The query processor has several parts, including the user interface (search box), the “engine” that evaluates queries and matches them to relevant documents, and the results formatter. More than 100 factors are considered while processing a query. Main part of this process is calculating the relevancy means relevant results.

4. Data retrieving
Once the result is calculated, next process is to retrieve that in a particular order. There are more than 100 factors for ranking the links in particular manner. Each search engine have their own algorithm for ranking.

5. SERP Result
After completing all the above process we will get the results of a query that we fired on search engine. Most of the search engines show it 10 links per page. The links that have good relevancy, reputation, brands etc. are shown above of all the other links.

I think you will get it now how search engines are works.

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