With the variety of database servers and user interface clients available for the electronic library, there are a corresponding number of network protocols supporting those clients. The primary protocols supported are the standard TCP/IP suite of telnet and FTP protocols. The conventional FTP and gopher clients communicate with the electronic library using the FTP protocol, the WWW and mosaic clients use the HTTP protocol.
The current POSTGRES interfaces, such as the POSTGRES "monitor" or "spog" and the Tcl/Tk browser implementations communicate with the POSTGRES DBMS using the POSTGRES libpq network interface. The libpq interface provides a low-level socket connection and transfers queries and data between the POSTGRES backend database server and the frontend clients using a set of ``c'' library routines.
As mentioned above, we are building support for the Z39.50 information retrieval communication protocol into the POSTGRES database system. Support for Z39.50 is already built into the Lassen client software described below. This Z39.50 client software has been tested using existing Z39.50 servers, such as the UC MELVYL system. Providing Z39.50 access to the database opens up the electronic library to any client program that uses this protocol. We believe that the Z39.50 protocol, as an official ANSI standard, has the potential to become the standard protocol for search and retrieval from electronic libraries. The ongoing enhancements to the Z39.50 standard appear to offer all of the capabilities of the current de facto standards like the HTTP protocol used in Mosaic.