Z39.50 and Other Standards for Information Exchange

Copyright © 2000 by R. E. Wyllys

Introduction

The Z39.50 standard for information exchange is an example, particularly pertinent to librarians and information scientists, of the general idea of technical standards. Shared technical standards are an indispensable tool of modern technological civilization.

Some of you may be aware of the consequences of the lack of common technical standards in such a mundane matter as that of electrical voltages, receptacles, and plugs. If you have ever traveled to Europe carrying with you an electric radio or razor, you will recall having to buy or borrow a transformer to handle the voltage mismatch between the U.S. and European electrical systems, as well an adapter for your radio or razor so that you could plug it into a European electrical receptacle. Most European countries use a 220-volt system, different from (and technically preferable to) the 110-volt American system, for distributing electrical power to homes, offices, and hotels,; and there are several different plug sizes and shapes in use in Europe. In a similarly annoying (to Americans) fashion, there are differences in television standards among the U.S., the U.K., And the continent of Europe. Just imagine what travel would be like in the U.S. if you had to worry about such matters in traveling from one state to another! That thought alone should be a persuasive argument for striving for shared standards for as many technical matters as possible.

Technical standards are established via standards organizations in each country. These organizations cooperate at the world-wide level in the International Organization for Standardization (ISO). The U.S. affiliate of ISO is the American National Standards Institute (ANSI). Of special relevance to LIS concerns in the U.S. is the National Information Standards Organization (NISO), a nonprofit association whose members represent the library, information services, and publishing sectors as professionals in these sectors and/or as representatives of manufacturers of equipment used in these sectors. ANSI has many other affiliates besides NISO; together, these affiliates cover a wide variety of types of standards.

NISO is an example of the way in which standards in general are developed. As an association of people interested professionally and/or commercially in a certain area, NISO develops technical standards for that area. Other associations and groups affiliated with ANSI work in similar fashion. Typically, an organization like NISO will have a number of different committees active at any given time. These committees, made up of people with technical expertise in the area with which the committee deals,

till a reasonably high level of agreement is reached within the concerned community on a new proposed standard.

Next, the committee recommends the adoption of the proposed standard to ANSI. In turn, ANSI circulates the proposed standard to all parties thought likely to be affected by the proposed standard, and further rounds of review, revision, and consensus-seeking ensue. Eventually, the finally revision of proposed standard is adopted as a interim national standard by ANSI, which publishes it, and submits it to ISO.

At the international level, ISO circulates the standard to other countries (whose standards organizations are usually already aware of the proposed standard and, quite often, have participated unofficially in its development) for their review and revision. Eventually, international consensus is reached, and the standard becomes an ISO standard.

It should be clear that this process can take years to complete with respect to any given standard--and it usually does take years. The length of the process has long been a serious problem. The difficulties have been exacerbated by the acceleration in the rate of technological change, especially in "high-tech" areas such as those of computers and telecommunications, areas with which the library, information services, and publishing sectors (among others) are closely concerned. All too often, de facto (i.e., widely used even though not official) standards developed by a particular manufacturer become so successful in the marketplace that the lengthy formal standards-setting process is by-passed.

A current example of the conflict between formal ("de jure") standards and de facto standards is the development of standards for HTML. Thanks to years of careful preparatory work by Tim Berners-Lee in developing the idea of hyperlinked text into a practical reality, realizable through the software that we know as the Web browser, HTML and browsers got off to a good start in 1993 with respect to formal standards. But since 1993 both Netscape and Microsoft have repeatedly made their own proprietary extensions to the agreed-upon HTML standard (the de jure standard) in order to try to gain advantage in the marketplace. One result is that Internet Explorer and Netscape interpret certain features of Webpages differently, and this causes continuing problems for Webpage designers. In his recent book (see Endnote 1), Berners-Lee discusses this problem and others in the development of the World-Wide Web.

In the late 1980s and early 1990s, much effort was expended by people, organizations, companies, and government bodies toward defining and establishing open standards. The hope was that open standards would deter the tendency, exemplified by the success of Microsoft, toward allowing many standards to be established de facto in ways that tend to stifle competition. This thrust toward open standards became known as the Open Systems Interconnection (OSI) movement. Its goal has been to provide standards to which all computer hardware and software vendors will adhere, so that the present multiplicity of interconnection and interface practices can be reduced, thus reducing the costs of designing and producing both hardware and software.

The U.S. government, through the National Institute of Standards and Technology (NIST, formerly known as the National Bureau of Standards), and many states, including Texas, have backed the OSI movement through contractual policies and legislation. A nonprofit corporation, the Corporation for Open Systems (COS), represents business interests in the OSI movement in the U.S.

The proponents of OSI defined seven levels at which standards need to be developed and used:

	Level 7	Application Layer	Deals with the interface between a user and the host computer: e.g., Microsoft Word translating a signal, initiated by the user's typing in a string of characters and then depressing the "Search" function key, into instructions to from Word to Windows 98 to try to find that string in a file.
	Level 6	Presentation Layer	Deals with syntactic representation of data: e.g., agreement on character code (e.g., ASCII, extensions to ASCII), data-compression and data-encryption methods, representations of graphics (e.g., files using the .PIC or .BMP formats).
	Level 5	Session Layer	Deals with creating and managing sessions when one application process requests access to another applications process (e.g., an Oracle client requesting data from an Oracle server).
	Level 4	Transport Layer	Deals with data transfer between end systems; flow control for two computers (e.g., how Netscape on your PC talks with the UT Libraries Online Web page). The TCP/IP (Transport Control Protocol/Internet Protocol) operates on this level.
	Level 3	Network Layer	Deals with establishing paths for data between a pair of computers and handling any switching among alternative routes between the computers, as well as with definitions of how to break files (or messages) up into individual packets of data, in such a way that the packets can be transmitted and then reassembled.
	Level 2	Data-Link Layer	Deals with the transmission of data frames (e.g., packets) over a physical link between network entities, including the incorporation of error-correction coding into the data frames.
	Level 1	Physical Layer	Deals with the physical (i.e., electrical and mechanical) aspects of transmitting data (e.g., voltage levels, pin-connector design, cable lengths, and grounding arrangements).

The seven levels of OSI continue to be useful to help clarify what kind of standards are involved in a given discussion of standards, but unfortunately the OSI movement has lost much of its impetus. Part of this loss of impetus has been a result of the explosive development of the World-Wide Web using the TCP/IP protocol, which, though now a standard, is inconsistent with open standards and the OSI movement for several technical reasons. The Dictionary of PC Hardware and Data Communications Terms, published by O'Reilly & Associates, Inc., comments thus on the causes and effects of this decline with respect to networks:

Although all major (and many minor) computer vendors now have OSI products, the OSI protocols were never widely implemented, and TCP/IP has become the first choice for multivendor networking, because of its:

Lower-cost and more-efficient implementation (less CPU time required, smaller programs)

Availability for most operating systems

Fast standardization and development cycle (usually using the Internet to facilitate communications) when a new requirement is identified

The Z39.50 (IR) Standard