RFC 2056 (rfc2056) - Page 1 of 7

Uniform Resource Locators for Z39

Network Working Group                                       R. Denenberg
Request for Comments: 2056                           Library of Congress
Category: Standards Track                                       J. Kunze
                                 University of California, San Francisco
                                                                D. Lynch
                                          SilverPlatter Information Ltd.
                                                                 Editors
                                                           November 1996


                  Uniform Resource Locators for Z39.50


Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

1. Introduction

   Z39.50 is an information retrieval protocol that does not fit neatly
   into a retrieval model designed primarily around the stateless fetch
   of data.  Instead, it models a general user inquiry as a session-
   oriented, multi-step task, any step of which may be suspended
   temporarily while the server requests additional parameters from the
   client before continuing.  Some, none, or all of these client/server
   interactions may require participation of the client user, depending
   only on the client software (the protocol itself makes no such
   requirements).

   On the other hand, retrieval of "well-known" data may be performed in
   a single step, that is, with a degenerate Z39.50 session consisting
   of exactly one protocol search request and response.  Besides the
   basic search sub-service, there are several ancillary sub-services
   (e.g., Scan, Result Set Delete).  Among the functions covered by
   combinations of the sub-services, two core functions emerge as
   appropriately handled by two separate URL schemes:  the Session URL
   and the Retrieval URL.

   Using two schemes instead of one makes a critical distinction between
   a Z39.50 Session URL, which opens a client session initialized for
   interactive use by the user, and a Z39.50 Retrieval URL, which opens
   and closes a client session to retrieve a specific information item.
   Making this distinction at the scheme level allows the user interface
   to reflect it on to the user, without requiring the user interface to



Denenberg, et. al.          Standards Track