15. Searching and Database on the Web

15.5. Retrieval

There are several ways to retrieval resources.

Direct retrieval. The database service and interface are closed protocols, and reside on a single mainframe computer. The search engine accepts query from the user with query language, and searches the database, and then retrieval resources or documents from the database, returns to the user. This is the searching and retrieval process for the traditional database.
Client-server internet service. The client (the user) send query to the server, the sever locates the resource or document and returns it to the client, and then the client displays it appropriately. The Web browser and the Web server are working this way. So are most search systems on the Web. The (indexing) database resides on a separated server from the client. The server can serves multiple queries from remote clients at one time. The server and the clients communicate with certain standard interface or protocols. For examples, TCP/IP and UDP are popular protocols used on Internet; HTTP protocol is used by the Web (or Mosiac, Netscape). Z39.50 search and retrieval standard is a communication protocol offically recognized by the American National Standards Organization (ANSI) National Information Standards Organization (NISO) as an international standard for communication. WAIS (Wide Area Information Server), the most popular Web indexing and searching method currently used on the Web, is based on the Z39.50 standard.

Sometimes the result set of searching is a list of URLs linked to the documents. In this case, the user can retrieve documents easily as the Web browser usually does.

Aixiang (I Song) Yao<ayao@csgrad.cs.vt.edu>
Last modified: Sat Oct 3013:15:51 1996