ANSI/NISO Z39.50-1992 ISSN: 1041-5653 (Revision of ANSI/NISO Z39.50-1988)
(This foreword is not part of American National Standard for Information Retrieval Application Service Definition and Protocol Specification for Open Systems Interconnection, ANSI/NISO Z39.50-1992. It is included for information only.)ANSI Z39.50-1992, American National Standard Information Retrieval Application Service Definition and Protocol Specification for Open Systems Interconnection, is a revision of ANSI Z39.50-1988. The 1988 and 1992 versions of Z39.50 are referred to as versions 1 and 2 respectively.
Version 1 was prepared by Committee D, "Computer-to-Computer Protocols," of NISO, the National Information Standards Organization. Committee D was organized to develop OSI application layer protocols for library applications, including an information retrieval protocol. The committee was disbanded after Z39.50 version 1 was approved. In 1989, the Z39.50 Maintenance Agency was formed, administered at the Library of Congress. Version 2 has been prepared by the Maintenance Agency to incorporate enhancements described in detail below.
In 1990 the Z39.50 Implementors Group (ZIG) was established. Members include manufacturers, vendors, consultants, information providers, and universities, who wish to access or provide access to various types of information, including bibliographic, full text, financial, public utility, chemical, and news. Thus, although the protocol was originally proposed (in 1984) for use with bibliographic applications, interest in Z39.50 as an information retrieval protocol is no longer limited to use with bibliographic information.
Z39.50 version 2 represents a consensus of the ZIG, which has in effect acted in an advisory capacity to the Maintenance Agency in the effort to develop version 2. ZIG Membership has been open to all interested parties.
Information Retrieval Protocol
The protocol specifies formats and procedures governing the exchange of messages between a requesting computer (the "origin") and a responding computer (the "target") to enable the origin to (1) request that the target search a database and identify records that meet specified criteria, and (2) request transmission of, and receive, some or all of the identified records.
The origin may initiate requests on behalf of a user who wishes to search a database located on the target system. The protocol addresses communication between corresponding information retrieval applications on the origin and target systems; it does not address interaction between the origin computer and user.
The Information Retrieval protocol provides the following basic capabilities: The origin may submit a Search request which includes a query, and parameters that determine whether or not records resulting from the search are to be returned as part of the response. The target responds with a count of records identified and possibly some or all of the records. The origin may then submit a Present request, requesting transmission of selected records. The origin assumes that records selected by the search request form an ordered set (the "result set") which may be referenced by sequential position within the set. Record order is determined by the target. The origin may request (for example) records one through four, and follow with a request for records four through eight, and then records two through three, etc. The origin may submit as many such Present requests as desired, and may then submit another Search request.
Optional capabilities include the following:
This standard mandates support of the "Type-1" query as a common format for the intersystem transmission of a search query. The "Type-1" query, fully specified in this standard, expresses a search query by individual search terms (or phrases) with a set of attributes for each. Attributes may specify, for example, type of term (subject, name, etc.), whether it is truncated, and its structure. The target is responsible for mapping these attributes to the logical design of the database.
Several terms may be combined in a Type-1 query, linked by Boolean operators. Terms and operators are expressed in Reverse Polish Notation.
The attributes associated with a search term belong to a particular attribute set, whose definition assigns integer values to various attributes. The definition is assigned a unique and globally recognized "attribute-set-id," an OSI Object Identifier, which is included within the query.
The process of assigning an OSI object identifier is called "registration." Appendix C defines and registers one attribute-set-id, "bib-1," which specifies various attributes that are useful for bibliographic queries. There is a mechanism to register additional attribute sets. Just as the bib-1 attribute set was developed by the bibliographic community, it is intended that attribute sets will be developed and registered as needed by other communities (for example, a chemical attribute set by chemists).
The protocol provides for the transfer of database records identified by a Search or Present request. The standard distinguishes two types of records, database and diagnostic records, which can occur in response messages from the target.
Appendix E registers object identifiers for various MARC formats, including USMARC, UKMARC, Norway MARC and CANMARC; these object identifiers accompany database records returned by the target. There is a provision for registration of additional record formats, including non-bibliographic formats.
Diagnostic records are similarly accompanied by an object identifier that identifies their format. Appendix D defines and registers one diagnostic record format, "bib-1," which includes various diagnostic codes that are useful for bibliographic applications. Additional diagnostic record formats may be registered.
Changes in Version 2
Z39.50 version 2 incorporates major enhancements to version 1, in two categories:
When SR was approved in 1991, incompatibilities between Z39.50 version 1 and SR remained:
The above differences are resolved in Z39.50 version 2. There will still be differences with SR, however. Z39.50 includes two services not yet in SR: access control and resource control. Some U.S. information providers cannot use Z39.50 if it does not include an access control service. Both services have been carefully incorporated so that an SR and Z39.50 version 2 origin/target pair may interwork transparently (i.e. the SR implementation would not be aware that its partner is a Z39.50 rather than SR implementation).
In general, implementors who plan to build Z39.50-specific features into their implementations, for use when interworking with a Z39.50 partner, would suppress these features when interworking with an SR partner. Thus, lack of these features in SR will not inhibit interoperability, although it might limit potential functionality. For example, information that an SR origin can receive from a Z39.50 target might be limited because the origin cannot respond to an access control request. (The same would be true of a Z39.50 origin which does not support access control--it is an optional service). The limitation would not owe to an incompatibility between origin and target implementations, but rather, because the target requires authentication and the origin cannot provide it.
Version 2 includes changes to the Resource Control facility. The origin will be able to request a resource control action or cancel an operation. These changes have been expressed as requirements by the ZIG.
Version 2 specifies five query types. Types 0,1, and 2 are identical to the three query types specified in SR. The "Type-0" query is designated "private," allowing two systems to use a private, mutually agreed upon query format. "Type-1" is described above. "Type-2" is as specified by ISO 8777. Z39.50 specifies two additional query types: "Type-100" is as specified by ANSI Z39.58, and "type-101" is for proximity searching. The latter is specified in Appendix G. Proximity searching is a feature that implementors recommended be incorporated into this version.
Z39.50 registers all information objects that are registered in SR: application context, abstract syntax, attribute set, diagnostic set, and record syntax definitions. In addition, Z39.50 attribute set and diagnostic set definitions contains additional attribute and diagnostic values that are "U.S. specific."
Z39.50 registers two additional object identifier classes: resource report format (for resource control, which is not yet in SR), and transfer syntax. The latter accommodates non-bibliographic databases. Z39.50 also provides a mechanism for registration of experimental and implementation-specific objects. The Z39.50 Maintenance Agency will act as registration authority for Z39.50 objects.
The generality of the protocol is intended to allow accommodation of new services as they are required. Some services being considered are:
Suggestions for improving this standard are welcome. They should be sent to the National Information Standards Organization, P. O. Box 1056, Bethesda, MD 20827, (301) 975-2814.
This standard was processed and approved for submittal to ANSI by the National Information Standards Organization. NISO approval of this standard does not necessarily imply that all Voting Members voted for its approval. At the time it approved this standard, NISO had the following members:
American Association of Law Libraries Gary J. Bravy American Chemical Society Robert S. Tannehill, Jr. Leon R. Blauvelt (Alt) American Library Association Myron Chace Sally McCallum (Alt) American Pyscological Association Lois Granick Maurine F. Jackson (Alt) American Society for Information Science Clifford Lynch American Society of Indexers Jessica Milstead Patricia S. Kuhr (Alt) American Theological Library Association Raymond Vandegrift Apple Computer, Inc. Karen Higgenbottom Art Libraries Society of North America Patricia J. Barnett Pamela J. Parry (Alt) Association of American Publishers (AUP) Sandra K. Paul Thomas D. McKee (Alt) Association of American University Presses (AAUP) Mary Lou Menches Association of Information and Dissemination Centers ASIDIC Bruce H. Kiesel Association of Information and Image Management AIIM Mary Courtot Association of Jewish Libraries Bella Hass Weinberg Pearl Berger (Alt) Association for Recorded Sound Collections (ARSC) Donald McCormick Barbara Sawka (Alt) Association of Research Libraries (ARL) Duane E. Webster AT&T Bell Labs George E. Grant M. E. Brennan (Alt) Baker & Taylor Books Christian K. Larew Stephanie Lanzalotto (Alt) Book Manufacturers' Institute Douglas Horner Catholic Library Association Michael B. Finnerty CLSI, Inc. Bob Walton Susan Stearnes (Alt) Colorado Alliance of Research Libraries (CARL) Ward Shaw Council of National Library of Information Associations Thomas J. Kemp Data Research Associates, Inc. Michael J. Mellinger James Michael (Alt) Dynix Rick Wilson EBSCONET, Inc. Sharon Cline McKay Mary Beth Vanderpoorten (Alt) Engineering Information, Inc. Eric Johnson Mary Berger (Alt) The Faxon Co., Inc. Fritz Schwartz Joe Santosuosso (Alt) Gaylord Information Systems Robert Riley Bradley McLean (Alt) IBM Corporation Peggy Federhart Indiana Cooperative Library Services Authority (INCOLSA) Barbara Evans Markuson Janice Cox (Alt) Library Binding Institute Sally Grauer Library of Congress Henriette D. Avram Sally H. McCallum (Alt) Mead Data Central Peter Ryall Dave Withers (Alt) Medical Library Association Rick B. Forsman Raymond A. Palmer (Alt) MINITEX Anita Anker Branin William DeJohn (Alt) Music Library Association Lenore Coral Geraldine Ostrove (Alt) National Agricultural Library Joseph H. Howard Gary K. McCone (Alt) National Archives and Records Administration Alan Calmes National Institute of Standards and Technology (NIST), Office of of Information Services, Research Information Center Marietta Nelson National Library of Medicine Lois Ann Colaianni OCLC, Inc. Kate Nevins Don Muccino (Alt) OHIONET Joel Kent Greg Pronevitz (Alt) Optical Publishing Association John Nairn R. Bowers (Alt) PALINET James E. Rush Pittsburgh Regional Library Center (PRLC) H. E. Broadbent III Readmore Academic Services Sandra Gurshman Dan Tonkery (Alt) The Research Libraries Group, Inc. RLG Wayne Davison Kathy Bales Society of American Archivists to be appointed Special Libraries Association SLA Audrey Grosch SUNY/OCLC Network Glyn T. Evans David Forsythe (Alt) UMI Don Willis Unisys Corporation Michel Ridgeway James Thomas (Alt) U.S. Department of Commerce Printing & Publishing Division William S. Lofquist U.S. Department of Defense, Army Library Management Office Dorothy Fisk McDysan Diane Zehnpfennig (Alt) U.S. Dept. of Defense Defense Technical Information Center (DTIC) Claire Tozier Gretchen Schlag (Alt) U.S. Dept. of Energy, Office of Scientific & Technical Information Mary Hall Nancy Hardin (Alt) U.S. ISBN Maintenance Agency Emery Koltay U. S. National Commission on Libraries and Information Science (NCLIS) Peter Young Sandra N. Milevski (Alt) VTLS, Inc. Vinod Chachra H. W. Wilson Company George I. Lewicky Ann Case (Alt)
At the time NISO approved this standard, the following individuals served on its Board of Directors:
James E. Rush, Chairperson PALINET Michael J. Mellinger, Vice Chair/Chair-elect Data Research Associates Paul Evan Peters, Immediate Past Chairperson New York Public Library Heike Kordish, Treasurer New York Public Library Patricia R. Harris, Executive Director National Information Standards Organization Directors-Representing Libraries Lois Ann Colaianni National Library of Medicine Susan Vita Library of Congress Shirley Kistler Baker Washington University Directors-Representing Information Services Lois Granick American Psychological Association Michael J. McGill Ameritech Wilhelm Bartenbach Engineering Information, Inc. Directors-Representing Publishing Peter J. Paulson OCLC/Forest Press Constance U. Greaser The RAND Corporation Marjorie Hlava Access Innovations, Inc.