Search engines can be divided into three in its work. They are full-text search engines, a directory index class search engine (SEARCH INDEX / DIRECTORY), and Meta Search Engine.
■ Full-text search engine
The full-text search engine is a veritable search engine, and the foreign representative representative of Google, Fast / AllTheweb, Altavista, Inktomi, Teoma, Wisenut, etc., domestic famous Baidu. They are all related records that match the user query criteria by the information created by the information (mainly web text) information (mainly web text), and then press the result to the user in a certain arrangement order, so they It is a real search engine.
From the perspective of search results, the full-text search engine can be divided into two, one is a "indexer", commonly known as "spider" program or "robot" program, and built The web database, the search results are called directly from their own database, as mentioned above, the other is the database of other engines, and arranges search results in a custom format, such as the LYCOS engine.
■ Directory Index
The directory index has a search function, but it is not a real search engine in strict sense, just a list of websites that are classified by the directory. Users can completely do keywords (Keywords) queries, only relying on classified directorys, you can also find information. The most representative of the catalog index is the famous Yahoo Yahoo. Other famous Open Directory Project (DMOZ), Looksmart, About, etc. Domestic Sohu, Sina, Netease Search also belong to this.
■ Meta search engine (META SEARCH ENGINE)
The meta search engine is searched on other multiple engines while receiving user query requests and returns the result to the user. The famous meta-search engine has InfoSpace, Dogpile, Vivisimo et al (yuan search engine list), and the Chinese sector search engine is a representative Search Search Engine. In terms of search results, some are arranged directly on the source engine, such as dogpile, and some will rearrange the results according to the custom rules, such as Vivisimo.
In addition to the above three major engines, there are still several non-mainstream forms:
1. Collection Search Engine: The engine that Hotbot launched at the end of 2002. This engine is similar to the META search engine, but the difference is that it is not to call multiple engines while selecting the four engines provided, so it is more exactly the "collection" search engine.
2, portal search engine: such as AOL Search, MSN Search, although the search service is provided, but there is no network database without a classified directory, and its search results are completely from other engines.
3, Free For ALL LINKS, ALFA: This type of website is generally simply scrolling the link entry, and there is a simple partial classification directory, but the scale is much smaller than the directory of Yahoo.
Since the above websites provide a search query service for users, we usually collect them as search engines.
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