Based on the different ways of information collection and service provision, search engines can be divided into the following four categories.
1. Classification catalog search engine
Classification catalog search engines collect information manually or semi-automatically. After the editor reviews the information, they manually form an information summary and place the information in a predetermined classification framework. The information is mostly oriented to websites, providing directory browsing services and direct retrieval services. The characteristics of this type of search engine are accurate information and high navigation quality; the disadvantages are that it requires manual intervention, large maintenance, large amount of information, and untimely information updates. The representative of this type of search engine is Sohu.
2. Robot search engine
Robot search engines are a robot program called “spider” that automatically collects and discovers information on the Internet with a certain strategy. The indexer creates an index for the collected information, and the retriever enters the search index according to the user’s query and returns the query results to the user. Its service method is a full-text retrieval service for web pages. The advantages of this type of search engine are large amount of information, timely updates, and no need for manual intervention; the disadvantages are that too much information is returned, there is a lot of irrelevant information, and users must filter from the results. Representatives of this type of search engine are Google, Baidu, etc.
3. Meta search engine
A meta search engine does not have its own data, but submits the user’s query request to multiple search engines at the same time, and returns the returned results to the user as its own results after deleting duplicates, re-ranking, etc. Its service mode is full-text retrieval for web pages. The characteristics of this type of search engine are that the amount of information returned is larger and more complete, but the function of the search engine cannot be fully utilized, and users need to do more screening. Representatives of this type of search engine are Web Crawler, InfoMarket, etc.
4. Integrated search engine
The integrated search engine has the simplest function. It does not require special core technology, nor does it have its own index database. It cannot even filter and re-rank the results. It just connects multiple search engines at the same time on a browsing page. Users can choose some or all of the search engines when searching. By entering keywords once, they can get the search results of multiple search engines.