Search engine Classification-search engine technology

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. The early search engine is to collect the address of the resource server in the Internet, and it is divided into different directories by the types of the resources provided by them, and then the classification is done on the same level. People want to find the information they want to enter the category layer by level, you can finally reach the destination, find the information they want. The information is mostly web-oriented,
Provides 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 type of search engine representative is: YAHOO, Open directory, the most representative of the domestic Sohu classification directory.
This is the early form of the Internet search engine, still occupies an important position. Yahoo is from a single search engine development to now have E-commerce, news information Services, personal free e-mail services, such as a variety of network services,
2. Machine search engine. The programs run by large-scale machines automatically collect and discover information in the Internet according to a certain strategy, indexing the information collected by the indexer, retrieving the index library according to the user's query input, and returning the query results 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, may have a lot of irrelevant information, the user must filter from the result. This type of search engine representatives are: AltaVista, Excite, InfoSeek, Inktomi, FAST, Lycos,,alltheweb, ask Jeeves, Google, the most representative of the domestic is: Baidu, Skynet, Openfind.
The shortcoming of the catalog search engine is becoming more and more obvious with the growth of the network information. The need to search for information on the Internet has made research institutions engaged in machine search and companies that provide search services exceptionally prosperous after 1995.
3. Meta search engine. Such search engines do not have their own data, it will be 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. This kind of search engine's representative is WebCrawler, in the actual application effect is not ideal.