Search Engines List

A search engine is a computer system that searches for files stored on web servers with its "spider" (or web crawler). An example is Internet search engines (some look only to the Web but also looking at other news services such as Gopher, FTP, etc.) When asked for information about a topic. The searches were done with key words or topics hierarchical tree, the search result is a list of Web addresses mentioned in the issues related to the keywords searched.

As they operate automatically, search engines generally contain more information than directories. However, the latter also must be built from searches (not automated) or from warnings given by the creators of pages (which can be very limiting). Good directories combine both systems. Today internet has become a tool for finding information quickly, to do the search engines that have emerged are a search engine that helps us find information quickly on any topic of interest, in any area of science, and anywhere in the world.

Classification

Search engines can be classified into two types:

  • Indexes: These systems search by subject or category hierarchy (although systems typically include keyword search). This database of Web addresses made "manually", ie, people who are responsible for assigning each site to one category or theme.
  • Bots search engines: These systems search for keywords. Databases are automatically incorporated into web pages by "robots" search on the net.

Types of Search Engines

Hierarchical search engines (Spiders)

    They navigate through the pages to collect information about the contents of the pages. When you are looking for information on a search engine, it checks its database and presents results ranked by relevance. Of the websites, search engines can store from the home page, all pages that reside on the server.

    If you want a word such as "computers", the results offered by the search engine will return pages that contain this word in any part of your text. If you believe a site is important for the user, they tend to register them all. If you do not believe in it, only store one or more pages.

    Every so often, the other sites reviewed to update the contents of your database, so can the search results are outdated.

    The hierarchical search engines have a collection of simple and powerful programs with different tasks. They are usually divided into three parts: Programs that explore the red-spiders (spiders) - those who build the database and used by the user, the software that operates the database.

    If paid, it can appear on the front pages of results, although the major search engines define these results and indicate the user that is sponsored or sponsored results. So far, apparently, this form of advertising is explicitly stated. Hierarchical seekers have been forced to sell this type of advertising revenue to continue offering consumers the service for free.

    Examples of spiders: Google, Bing, Hotbot.

Directories

This is an inexpensive technology which is widely used by large number of scripts on the market. It does not require too many computer resources. Instead, it requires more human support and maintenance.

  • The algorithms are much simpler, presenting information on the sites registered as a collection of directories. It does not require traveling web sites and storing their content. They just register some of the data of our website, as the title and description which are introduced when registering the site in the directory.
  • The search results will be determined by the information supplied to the directory when registering the site. However, unlike the other, are reviewed by human operators, and classified according to categories, so it is easier to find pages on the subject of our interest.
  • Rather than seeking information on page content, the results will be presented with reference to the contents and theme of the site.
  • Their technology is very cheap and easy.

Examples of directories: Old directories, Open Directory Project, Yahoo, Terra (formerly Olé). Now, both use hierarchical search technology, and Yahoo retains its directory. Search Portal is a directory.