Using the Z39.50 Information Retrieval Protocol (RFC1729)
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2019-Feb-12
Internet Society Requests For Comment (RFCs)
This memo describes an approach to the implementation of the ANSI/NISO Z39.50-1992 Standard for Information Retrieval in the TCP/IP environment which is currently in wide use by the Z39.50 implementor community. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.
Network Working Group C. Lynch Request for Comments: 1729 University of California Category: Informational Office of the President December 1994
Using the Z39.50 Information Retrieval Protocol in the Internet Environment
Status of this Memo
This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
This memo describes an approach to the implementation of the ANSI/NISO Z39.50-1992 Standard for Information Retrieval in the TCP/IP environment which is currently in wide use by the Z39.50 implementor community.
Z39.50 is a US national standard defining a protocol for computer- to-computer information retrieval that was first adopted in 1988  and extensively revised in 1992 . It was developed by the National Information Standards Organization (NISO), an ANSI-accredited standards development body that serves the publishing, library, and information services communities. The closely related international standard, ISO 10162 (service definition)  and 10163 (protocol) , colloquially known as Search and Retrieve or SR, reached full International Standard (IS) status in 1991. Work is ongoing within ISO Technical Committee 46 Working Group 4 Subgroup 4 to progress various extensions to SR through the international standards process. The international standard is essentially a compatible subset of the current US Z39.50-1992 standard. Z39.50 is an applications layer protocol within the OSI reference model, which assumes the presence of lower-level OSI services (in particular, the presentation layer ) and of the OSI Association Control Service Element (ACSE)  within the application layer.
Many institutions implementing this protocol chose, for various reasons, to layer the protocol directly over TCP/IP rather than to implement it in an OSI environment or to use the existing techniques that provide full OSI services at and above the OSI Transport layer on top of TCP connections (as defined in RFC 1006  and implemented, for example, in the ISO Development Environment
Lynch [Page 1]
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 som...