Презентация "Computer Assisted Retrieval System"

Computer Assisted Retrieval System

History

• The first computer program to search the Internet was the Archie program. It was created in 1990 by Alan Emtage, Bill Heelan and J. Peter Deutsch, students of computer science at McGill University in Montreal. The program downloaded lists of all files from all available anonymous FTP-servers and built a database in which it was possible to search by file names. However, the Archie program did not index the contents of these files, since the amount of data was so small that everything could be easily found manually.

• Google took on the idea of ​​selling keywords in 1998, then it was a small company that provided a search engine for the address goto.kom. This step marked for search engines the transition from competition to each other to one of the most profitable commercial enterprises on the Internet. Search engines began to sell the first places in search results to individual companies.

• The search engine Google has been prominent since the early 2000s.
• Microsoft first launched the Microsoft Network Search (MSN Search) search engine in the fall of 1998, using the search results from Inktomi. Very soon in early 1999, the site began to display the issue of Loksmart, mixed with the results of Inktomi. Shortly (in 1999), MSN search used search results from AltaVista. In 2004, Microsoft began the transition to its own search technology using its own search robot - msnbot [en]. After the rebranding by Microsoft, on June 1, 2009, the search engine Bing was launched. July 29, 2009 Yahoo! and Microsoft signed an agreement under which Yahoo! Search worked on the basis of Microsoft Bing technology. At the time of 2015, the union of Bing and Yahoo! gave the first real fruit. Now Bing takes 20.1% of the market, and Yahoo! 12.7%, which in general is 32.60% of the total search market in the United States according to data from different sources

How does the search engine work?

• The search engine analyzes the content of each page for further indexing. An indexer is a module that analyzes a page by first breaking it into parts using its own lexical and morphological algorithms. The index allows you to quickly find information on the user's request. A number of search engines like Google store the entire page or part of it, the so-called cache, as well as various information about the web page. Using the cache helps speed up the extraction of information from already visited pages Cached pages always contain the text that the user specified in the search query. In addition to using cached pages to speed up the search, pages in the cache can contain information that is no longer available anywhere.

• The usefulness of a search engine depends on the relevance of the pages it finds. Although millions of web pages may include a certain word or phrase, some of them may be more relevant, popular or authoritative than others. Most search engines use ranking methods to bring "best" results to the top of the list. Search engines decide which pages are more relevant, and in which order the results should be displayed, in different ways. Search methods, like the Internet itself, change over time. So there were two main types of search engines: systems of predefined and hierarchically ordered keywords and systems in which an inverted index is generated based on text analysis.

Types of search engines

1)The systems using search robots

They consist of three parts: the crawler ("bot", "robot" or "spider"), the index and software of the search engine. The crawler is needed to bypass the network and create lists of web pages. Index - a large archive of copies of web pages. The purpose of the software is to evaluate the search results.

2)Human-managed systems

These search engines get lists of web pages. The catalog contains the address, title and brief description of the site. The resource directory looks for results only from the descriptions of the page submitted to it by the webmasters. The advantage of directories is that all resources are manually checked, hence, the quality of the content will be better than the results obtained by the first type system automatically. But there is also a drawback - the updating of catalog data is done manually and can significantly lag behind the actual state of affairs. The page ranking can not be instantly changed. Examples of such systems include the directory of Yahoo , Dmoz and Galaxy.

3)Hybrid systems

Such search engines as Yahoo, Google, MSN, combine the functions of systems using search robots, and systems controlled by humans.

4)Meta-systems

Metasearch systems combine and rank the results of several search engines. These search engines were useful when each search engine had a unique index, and the search engines were less "smart". Since now the search has much improved, the need for them has decreased. Examples: MetaCrawler [en] and MSN Search.

Search engine market