Most of us use search engines every day to search about particular query and search engines return some best results those are relevant to that query.Here we will see how search engines works?
Search engines work in three different phases
1. Web Crawling
Web search engine stores information about webpages which they retrieve from html itself.These pages are retrieved by web crawlers most of time we call as Spider.Web crawlers crawls site and follows each indexed link of every site.You can restrict these web crawlers from robot.txt which is made for these web crawlers. These crawlers then extract all the information about web page from title ,meta tags, headings & content and stores in database.
When user types a search query then first of all search engines check results in database file if they have already incurred query ,Google uses cache mechanism for that where they store result of search queries to minimize time.Increased search relevance makes these cached pages very useful, even beyond the fact that they may contain data that may no longer be available elsewhere.
When a user enters a query into a search engine (typically by using key words), the engine examines its index and provides a listing of best-matching web pages according to its criteria, usually with a short summary containing the document’s title and sometimes parts of the text. The index is built from the information stored with the data and the method by which the information is indexed. Unfortunately, there is not one search engine that allows to search documents by date. Most search engines support the use of the Boolean operators AND,OR and NOT to further specify the search query. Boolean operators are for literal searches that allow the user to refine and extend the terms of the search. The engine looks for the words or phrases exactly as entered. Some search engines provide an advanced feature called proximity search which allows users to define the distance between keywords. There is also concept-based searching where the research involves using statistical analysis on pages containing the words or phrases you search for. As well, natural language queries allow the user to type a question in the same form one would ask it to a human. A site like this would be ask.com.
Working of Search Engine is shown as below,
The usefulness of a search engine depends on the relevance of the result set it gives back. While there may be millions of web pages that include a particular word or phrase, some pages may be more relevant, popular, or authoritative than others. Most search engines employ methods to rank the results to provide the “best” results first. How a search engine decides which pages are the best matches, and what order the results should be
shown in, varies widely from one engine to another. The methods also change over time as Internet usage changes and new techniques evolve. There are two main types of search engine that have evolved: one is a system of predefined and hierarchically ordered keywords that humans have programmed extensively. The other is a system that generates an “inverted index” by analyzing texts it locates. This second form relies much more heavily on the computer itself to do the bulk of the work.
This is the process by which post of the search engines work now a days though we see many changes in algorithm and searching mechanism ,every search engine is focused on relevancy and better load time.