How search engines work

■ Full-text search engine
In the search engine Classification Section, we mentioned the concept that full-text search engines extract information from websites to create a web database. The search engine's automatic information collection function is divided into two types. One is regular search, that is, at intervals of time (such as 28 days for Google), the search engine actively sends a "Spider" program to search Internet sites within a certain IP address range, once a new website is found, it automatically extracts the website information and adds the website address to its own database.
The other is to submit a website search. The website owner submits a website to the search engine. within a certain period of time (ranging from 2 days to several months), the website owner sends a "Spider" program to your website, scan your website and store the related information in the database for user query. As the search engine index rules have changed a lot in recent years, it is not guaranteed that your website can enter the search engine database when you submit a website. Therefore, the best way to obtain more external links is, this gives search engines more opportunities to find you and automatically include your website.

When a user searches for information using keywords, the search engine searches for information in the database. If a website matches the content required by the user, A special algorithm is used to calculate the relevance and ranking level of each webpage based on the keyword matching degree, location/frequency, and link quality of the webpage, then, the links are returned to the user in order based on the correlation level.

■ Directory Index
Compared with the full-text search engine, the Directory Index has many differences.

First, the search engine is an automatic website search, and the Directory Index is completely dependent on manual operations. After a user submits a website, the directory editor will view your website in person and decide whether to accept your website based on a set of custom criteria or even the subjective impressions of the editors.

Second, when a search engine includes a website, the website can be successfully logged on as long as it does not violate the relevant rules. However, Directory Indexing requires a much higher website. Sometimes it is not necessarily a success even if you log on multiple times. Especially for Yahoo! Such a super index makes logon more difficult. (Because you have logged on to Yahoo! It is the most difficult, and it is a must for online marketing for sellers. So we will introduce the skills for logging on to Yahoo later ). In addition, when logging on to the search engine, we generally do not need to consider the classification of the website. When logging on to the Directory Index, you must put the website in the most appropriate directory (directory ).

Finally, the information of each website in the search engine is automatically extracted from the user's webpage. Therefore, from the user's perspective, we have more autonomy; the Directory Index requires that you manually enter the website information, and there are various restrictions. What's more, if the staff thinks that the directory and website information of your submitted website is inappropriate, they can adjust it at any time. Of course, they will not discuss it with you in advance.

As the name implies, a Directory Index stores websites in different directories. Therefore, when querying information, you can select keywords for search or search by category directory layer by layer. For example, if you search by keyword, the returned results are the same as those of the search engine. The website is also sorted based on the degree of Information Association, but there are more human factors. If you search by hierarchical directory, the ranking of websites in a directory is determined by the order of titles and letters (with exceptions ).

At present, search engines and directory indexes are penetrating each other. Some pure full-text search engines now provide Directory Search, for example, Google uses the Open Directory directory to provide category query. Like Yahoo! These old directory indexes expand the search scope through cooperation with search engines such as Google. In the default search mode, some Directory Search Engines first return websites matching their directories, such as search for foxes, Sina, and Netease in China; in addition, Web search, such as Yahoo, is used by default. For more information, see http://www.chinaddv.com/