ANSI/NISO Z39.50 is the American National Standard Information Retrieval Application Service Definition and Protocol Specification for Open Systems Interconnection. The National Information Standards Organization (NISO), an American National Standards Institute (ANSI) accredited standards developer that serves the library, information, and publishing communities, approved the original standard in 1988 (referred to as Z39.50-1988 or Version 1). NISO published a revised version of the standard in 1992 (referred to as Z39.50-1992 or Version 2).
ANSI/NISO Z39.50 defines a standard way for two computers to communicate for the purpose of information retrieval. Z39.50 makes it easier to use large information databases by standardizing the procedures and features for searching and retrieving information. Specifically, Z39.50 supports information retrieval in a distributed, client and server environment where a computer operating as a client submits a search request (i.e., a query) to another computer acting as an information server. Software on the server performs a search on one or more databases and creates a result set of records that meet the criteria of the search request. The server returns records from the result set to the client for processing. The power of Z39.50 is that it separates the user interface on the client side from the information servers, search engines, and databases. Z39.50 provides a consistent view of information from a wide variety of sources, and it offers client implementors the capability to integrate information from a range of databases and servers.
ANSI/NISO Z39.50 can be implemented on any platform. This means that Z39.50 enables different computer systems -- with different operating systems, hardware, search engines, database management systems -- to interoperate and work together seamlessly. A Z39.50 implementation enables one interface to access multiple systems providing end users with nearly transparent access to other systems. Users access multiple systems with the familiar commands and displays of their own local systems. New commands and search techniques do not have to be learned. The results of the search are presented on the local system -- again, in the formats and styles users are accustomed to.
One of the strengths of ANSI/NISO Z39.50 is that it is an American National Standard. NISO developed and maintains Z39.50 using consensus procedures approved by ANSI, the principal coordinator of voluntary standardization in the United States. Z39.50 is not a proprietary standard and will continue to be responsive to the needs of the implementors that use the standard and the information consumers that benefit from its implementation.