Uncover the mystery, search engine theory-search engine technology

On the vast Internet, especially on the Web (World Wide Web), there is no search and no internet access. Network worm Friends, do you know the search engine? How do they work? Which search engines do you use? Today I will talk to you about the topic of search engine.
　　
I. Classification of search engines
We can call it a search engine by getting the Web page data, the ability to build a database and provide a query system. Depending on how they work, they can be grouped into two basic categories: Full-text Search engines (fulltext search Engine) and catalog directory.
Full-Text search engine database is to rely on a call "network Robot (Spider)" or "network spider (crawlers)" software, through a variety of links on the network automatically obtain a large number of Web page information content, and according to the rules of the analysis of the formation. Google, Baidu are more typical of the Full-text search engine system.
Classification directory is through the manual collection of Web site data to form a database, such as Yahoo China and the domestic Sohu, Sina, NetEase classification directory. In addition, some navigation sites on the web can also be attributed to the original categories, such as "home of the Web site" (http://www.hao123.com/).
Full-text search engines and categories are used in each of the length. Full-text search engine because of the software, so the capacity of the database is very large, but its query results are often not accurate; The catalog relies on manual collection and collation of the site, can provide more accurate results of the query, but the collection of content is very limited. To complement each other, now many search engines, both provide both types of inquiries, the general search engine query called "All Sites" or "all sites", such as Google's full-text search (http://www.google.com/intl/zh-CN/) , refer to the classification directory query called search "category directory" or search "classified site", such as Sina Search (http://dir.sina.com.cn/) and Yahoo China Search (http://cn.search.yahoo.com/dirsrch/).
On the Internet, the two types of search engine integration, but also generate other search services, here, we also call them search engines, there are two main categories:
⒈ meta search (meta search Engine). Such search engines generally do not have their own network robots and databases, their search results are by invoking, controlling and optimizing the search results of many other independent search engines and in a unified format in the same interface display. Although the meta search engine does not have "network robot" or "network Spider", and has no independent index database, it has its own research and development feature meta search technology in the aspects of Retrieval request submission, retrieval interface proxy and search result display. such as "Metafisher Meta search Engine"