RFC 1729 (rfc1729) - Page 2 of 8

Using the Z39

RFC 1729      Using the Z39.50 in the Internet Environment December 1994


   software). These reasons included concerns about the size and
   complexity of OSI implementations, the lack of availability of mature
   OSI software for the full range of computing environments in use at
   these institutions, and the perception of relative instability of the
   architectural structures within the OSI applications layer (as
   opposed to specific application layer protocols such as Z39.50
   itself). Most importantly, some of these institutions were concerned
   that the complexity introduced by the OSI upper layers would outweigh
   the relatively meager return in functionality that they were likely
   to gain. Thus, for better or worse, the decision was taken to
   implement the Z39.50 protocol directly on top of TCP (with the
   understanding that this decision might be revisited at some point in
   the future).

   During 1991-1993, a group of implementing institutions agreed to
   participate in the Z39.50 Interoperability Testbed project (sometimes
   referred to by the acronym "ZIT") under the auspices of the Coalition
   for Networked Information (CNI). Their primary objective was to
   encourage the development of many interoperable Z39.50
   implementations running over TCP/IP on the Internet. By mid-1993, a
   number of independent Z39.50 implementations were operational and
   able to interoperate across the Internet.

   The Library of Congress, in its role as the Z39.50 Maintenance Agency
   for NISO, maintains a registry of the implementors [8], which
   includes members of the Z39.50 interoperability testbed.

   This document describes implementation decisions by current
   implementors of Z39.50 in the Internet environment. These have been
   proven within the ZIT project and are being used by most of the
   members of the Z39.50 Implementors' Group (ZIG), an informal group
   that meets quarterly to discuss implementation and interoperability
   issues and to develop extensions to the Z39.50 protocol targeted for
   inclusion in future versions of the standard. Intended as a guide for
   other implementors who seek to develop interoperable Z39.50
   implementations running over TCP/IP, this document focuses on issues
   related to TCP/IP, and it does not address other potential
   interoperability problems or agreements that have been reached among
   the implementors to address these problems. It does include a few
   notes about extensions to the existing Version 2 protocol that are
   being used in the implementor community which have interoperability
   implications.  Potential implementors of Z39.50 should subscribe to
   the Z3950IW LISTSERV [9] to obtain information specific to the Z39.50
   protocol and extensions under development as well as details of
   current implementations.






Lynch