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In September 1990, the U.S. Department of Education's Library Technology and Cooperation Grants Program awarded a three‐year grant to the Florida Center for Library Automation (FCLA), an agency of the Florida State University System, to develop software adhering to the ANSI Z39.50 Information Retrieval protocol standard. The Z39.50 software was to operate over the Open Systems Interconnect (OSI) communications protocols and be integrated with FCLA's NOTIS system, which is shared by all nine state universities in Florida. In order to test the correctness of its Z39.50 software, FCLA sought out other library software developers who would be willing to develop Z39.50 systems of their own. As part of this process, FCLA helped to found the Z39.50 Implementors' Group (ZIG), which has since gone on to improve the standard and promote Z39.50 implementations throughout much of the North American library systems marketplace. Early on in the project, it became apparent that TCP/IP would be a more heavily used communications vehicle for Z39.50 messages than OSI. FCLA expanded its design to include TCP/IP and, by the end of the grant in September 1993, will have a working Z39.50 system that can communicate over both OSI and TCP/IP networks.

The nature of information retrieval applications, the Z39.50 protocol, and its relationship to other OSI protocols are described. Through Z39.50 a client system views a remote server's database as an information resource, not merely a collection of data. Z39.50 allows a client to build queries in terms of logical information elements supported by the server. It also provides a framework for transmitting queries, managing results, and controlling resources. Sidebars describe the Z39.50 Implementors Group, the Z39.50 Maintenance Agency, and international standards for OSI library application protocols.

What started as a pilot project in 1985 has become a successful online tool for resource sharing today. The IRVING Network gives libraries with incompatible computers the ability to access each other's current catalog, determine circulation status, and process interlibrary loan transactions, while maintaining the integrity of their own systems. Although communication standards are evolving through the efforts of the Linked Systems Project, cooperative vendor programs in AVIAC, and Standards Committee D of NISO, it may be years before the majority of vendors can implement the standards and offer network packages to libraries across the country. In the meantime, the IRVING Library Network presents a practical, working solution to the problem of linking heterogenous library systems.

This special “theme” issue of Library Hi Tech is devoted to Open Systems Interconnection. The editor is Ray Denenberg, of the Library of Congress. Eleven articles cover the basic OSI platform, applications, support areas, and implementation. The basic OSI platform consists of protocols for the seven layers, including support for file transfer and message handling. Three articles describe network applications and the corresponding OSI services and protocols. “Information Retrieval as a Network Application” describes the ANSI Z39.50 protocol. Another article describes the interlibrary loan protocol, which incorporates the sequences of messages that occur in distributed interlibrary loan transactions. An article about electronic data interchange describes the edi conceptual model being developed by ISO, and its relationship to OSI. Network management and directory services are two of the most important OSI support areas; individual articles cover these two topics. Implementation topics include profiles, testing, and products.

The upper three OSI layers support the communication requirements of applications, while the lower four layers provide reliable transmission of data. This article describes the lower four layers. First, though, a brief overview of the layered model is presented including a summary of the upper three layers. Then a description of the lower three layers is followed by a discussion of data communication standards associated with specific layers. Architectural concepts are then explored: hierarchy and abstraction within the layers, levels of dialogue, internetworking, end‐to‐end communication, analysis of layer four, and a discussion of connection‐oriented, connectionless, and message‐oriented protocols and applications. The article concludes with a comparison of OSI and the de facto industry protocols, TCP/IP, which are currently used within the Internet.

The Linked Systems project (LSP) is directed towards implementing computer‐to‐computer communications among its participants. The original three participants are the Library of Congress (LC), the Research Libraries Group (RLG), and the Western Library Network (WLN, formerly the Washington Library Network). The project now has a fourth participant, the Online Computer Library Center (OCLC). LSP consists of two major components. The first component, Authorities Implementation, is described in Library Hi Tech issue 10 (page 61). The second component, the Standard Network Interconnection (SNI), is the specification of the LSP protocols, and the implementation of these protocols on the participant systems. Protocol specification was a joint effort of the original three participants (LC, RLG, and WLN) and was described in Library Hi Tech issue 10 (page 71). Implementation, however, has consisted of individual efforts of the (now) four participants. This four‐part report focuses on these individual implementation efforts.

Vendors who are implementing the Standard Network Interconnection (SNI) protocols for computer to computer communications can now test their implementation against the LSP/SNI Test Facility, which has been developed by the Library of Congress. The facility is intended to verify the correct functioning of the SNI protocols for the Open System Interconnection (OSI) layers. The development and use of the Test Facility are discussed.

The Linked Systems Project, directed toward implementing computer‐to‐computer communications, consists of two major program components. One component is the development of the Standard Network Interconnection. The other is the creation of a practical application —Authorities Implementation—which was discussed in the preceding article. This discussion of the Linked Systems Project covers the design and implementation of the Standard Network Interconnection. The article on “Open Systems Interconnection” in Library Hi Tech, No. 9, should be read as an introduction to this topic (and article).

The need for standards allowing computer‐to‐computer communication, and examples of technical issues are discussed. The framework of the Open Systems Interconnection Reference Model, consisting of seven layers, each performing a distinct and defined function, is explained and illustrated. Sidebars feature: 1) public data networks and X.25, 2) OSI standards, and 3) the OSI layer functions. A glossary is included.

The Western Library Network software, installed at such libraries and networks as the National Library of Australia, the National Library of New Zealand, The British Library and the Universities of Illinois and Missouri, is also available through Biblio‐Techniques as a fully vendor‐supported system called BLIS. Currently installed at six major research libraries, BLIS supports an online union catalog; a catalog management facility, including authority control, acquisitions, and accounting control. Circulation and other modules are under development.