How the technology and development trend of search engine change-search engine technology

With the rapid development of the Internet, the increase of web information, users to find information in the ocean, like a needle in the haystack, search engine technology to solve the problem (it can provide users with information retrieval services). At present, search engine technology is becoming the object of research and development of computer industry and academia.
　
Search engine (Engine) is a technology that has been developed gradually since 1995 with the rapid increase of web information. According to a July 1999 article published in the journal Science, "Accessibility of web information" estimates that the world currently has more than 800 million web pages, more than 9T of effective data, and is still growing at a rate of doubling every 4 months. Users in such a vast ocean of information to find information, will inevitably be "in a haystack" without work and return.
　
Search engines are the technology that comes to solving this "trek" problem. Search engine to a certain strategy in the Internet to collect, find information, understanding, extraction, organization and processing of information, and to provide users with retrieval services, so as to play the purpose of information navigation. Search engine provides navigation service has become the Internet is very important network services, search engine site is also known as the "Network portal." Therefore, search engine technology has become the object of research and development in computer industry and academia. The purpose of this paper is to introduce the key technology of search engine briefly, so as to play a useful role.
　
First, classification
According to the different methods of information collection and service delivery, the search engine system can be divided into three main categories:
1. Catalog Search Engine: Collect information manually or in a semi-automatic manner, after the editors view the information, form a summary of the information, and place the information in a predetermined categorization framework. Most of the information is web-oriented, providing directory browsing services and direct retrieval services. This kind of search engine because has joined the human intelligence, therefore the information is accurate, the navigation quality is high, the shortcoming is needs the artificial intervention, the maintenance quantity is small, the information quantity is not timely. This kind of search engine's representative is: Yahoo, LookSmart, Open Directory, go guide and so on.
　
2. Robot search Engine: by a robot called Spider (Spider) in a certain strategy to automatically collect and find information in the Internet, by the indexer for the collection of information indexed, by the reader based on the user's query input to retrieve the index library, and return the results of the query to the user. Service mode is a web-oriented Full-text search service. The advantage of this kind of search engine is the information is big, update in time, need not human to intervene, the disadvantage is that the return is too much, have a lot of irrelevant information, the user must filter from the result. This type of search engine representatives are: AltaVista, Northern Light, Excite, InfoSeek, Inktomi, FAST, Lycos, Google, the domestic representative: "Skynet", leisurely travel, openfind and so on.
　
3. Meta search engine: This type of search engine does not have its own data, but the user's query request to multiple search engines at the same time, will return the results of repeated exclusion, reordering, and so on, as their results returned to the user. Service mode is web-oriented Full-text search. The advantage of this kind of search engine is that the information of the return result is bigger and more complete, the disadvantage is that the function of the search engine can not be fully used, the user needs to do more filtering. This kind of search engine's representative is WebCrawler, Infomarket and so on.