Everyone uses a search engine these days, because for any kind of information you need online, this is the platform to access. The search engine basically requests for data from a massive database of resources which are present online. Given the massive surge in Internet usage in the last two decades, a world without search engines like Google and Bing is unthinkable. Search engines are used both by people looking for information and by websites looking to get higher ranks for more traffic.
Different Types of Search Engines:
Depending on how they work, search engines can be of different types, namely crawler-based search engines, hybrid search engines, human powered directories, etc.
1.Crawler Based Search Engines: These typically use bots or web crawlers for “crawling” online content. They index new content and link it to the search databases. Every crawler based search engine will do the following before they show any search results:
- Crawl to fetch web pages which are available for the query. The bot or “spider” does this and frequency of crawling will depend on the search engine. It often takes some days between these “crawls” and this explains why you get to view old/deleted pages in search results. When crawling resumes, the results will display updated content.
- Indexing identifies the words which describe the page perfectly; these words/phrases are called keywords. If the crawler fails to understand a page meaning, it assigns it a lower rank.
- Calculates relevancy of each web page using the search string using different algorithms.
- Retrieves results and displays these in an order on your browser.
Common examples of crawler-based search engines are Google, Yahoo, and Bing. Some other frequently-used ones are DuckDuckGo and AOL.
2. Human Powered Directories: These are called open directory systems and rely on human-based activities to make listings. So, the site owner provides a brief description of the website to a directory; this is manually reviewed and then added to the right listing category or rejected. Yahoo! Directory was one such human powered directory that was replaced by automated search engines of the likes of Google.
3. Hybrid Search Engines: These make use of both manual indexing and crawler-based indexing to prepare lists of sites in search engine results. Search engines like the Google typically use crawlers as their main tool and human powered directories as the secondary tool. With human powered directories slowly becoming redundant, hybrid search engines are taking over. However, when a website is detected for spam activities, the owner needs to take corrective measures. The site is then resubmitted and manually reviewed.
4. Meta search engines: These will take results from that of other search engines and then combine these to produce one big listing. Common examples are Metacrawler, Dogpile, etc which are all meta search engines.
5. Specialty search engines: These have been designed for catering to demands of niche areas. You will come across many specialty search engine types like Yahoo Shopping, BizRate and PriceGrabber for shopping, NZ pages for local search, Freeparking for domain name search, etc.
