Page 2 - Difference between Spider,Crawler and Robot

So far I have studied these are complementary components of Search Engine. When ever a new page is introduced on the web, Search Engine follows these steps

1)Spider : It finds out new pages introduced and submits to the database
2)Indexer: Parses the content of the page and categorizes according to its importance like hyperlinks, bold and italic content, heading, Title, URL
3)Crawler: A semantic algorithm to find relevancy of an indexed page based upon its keyword frequency and proximity.

It can be thought of some initial stage of a compiler that parses a content and analyzes the content syntactically and semantically.
Robot I think is generic name to refer all of them. As Googlebot, yahoobot etc are one name to refer to its crawler and indexer.

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Often robot, crawler, scooter, spider are used in same sense. But there are minute difference. Robot is generic name. Spider, scooter are like browser program which automatically requests web pages from web servers as it is apparent from the name spider ie waving kind of function.
Indexer extracts the content that will be easier for search engine to parse and evaluate.
Crawling is the actual algorithm or mechanism that evaluates a web site.
For a general user all are same. But when you study working mechanism of search engine it has different steps of executions and hence different name has come. A few terms are parallel, I mean, different search engines call its program with different name. But all terms are not same. Please refer to search engine dictionaries and try understanding minute difference in their definition.

No hard feelings please. More we contemplate more we understand.
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