Download mwnbwbxjwjwvfjqkjsbdjwjdndbwhw and more Lecture notes Library science in PDF only on Docsity!
Library and Information
UNIT 11 LIBRARY AND INFORMATION Networks
NETWORKS
Structure
11.0 Objectives
11.1 Introduction
11.2 Basic Concepts and Terminology
11.2.1 Network Definition 11.2.2 Communication Networks’ 11.2.3 Computer Networks 11.2.4 Information Networks
11.3 Types of Networks
11.3.1 Network Objectives 11.3.2 Network Architecture 11.3.3 Network Applications
11.4 Development of Library Networking
11.4.1 Range of Network Services 11.4.2 Library Networks in USA and UK 11.4.3 Library and Information Networks in India 11.4.4 Non-Bibliographic Networks in India
11.5 Summary
11.6 Answers to Self Check Exercises
11.7 Key Words
11.8 References and Further Reading
11.0 OBJECTIVES
In Unit 10 of this Block, an attempt has been made to explain to you the concept of a `system' and what constitutes an Information storage and Retrieval system, particularly computer-based Information storage and Retrieval System, and its design and operational aspects.
In this Unit (Unit-11), let us try to understand the concept of `networks', especially, library and information networks-what they are, how they function, and their the role in the provision of information service to the users as also in the resource sharing activities.
After reading this Unit, you will be able to:
- understand the concept of computer networking in all its major forms;
explain the role of networking in the public domain; know the meaning of library and bibliographic networking; the role of networking in resource sharing and information services; and explain some of the current developments in networking taking place in the developed countries of the world.
11.1 INTRODUCTION
During the last decade, the importance of computer networks and telecommunications has grown tremendously.' Computers can now communicate with each other and with a range 'of peripheral devices, over distances with increasing speed and reliability. Technological advances in communication have
ushered in a new era not only of computer power but of access to 25
Information System and Networks
information services at least in those parts of the world that have been able to develop extensive and reliable telephone networks. The transmission over the telephone network, not only of voice but more recently also of text and simple illustration through telefacsimile, laid the foundations for this age in which communications is taken for granted in developed countries. Computer assisted information networks remove the barriers of space and time which previously limited the communicative abilities of individuals. The developing global interconnectivity of networks can bring people of like interests together, who would otherwise never meet because of separated geographical locations. At the organisation level, local networking supports the ability of small teams to work together directly through a computer, application. Organisations and governments are now able to perceive information and its exchange as a resource to support innovation and creativity. Information professionals have the potential to play an important role in these developments. For example, the skills and understanding of the information professionals are particularly appropriate to the task of designing and supporting communications systems which facilitate them to interface between information and user. It may be mentioned here that the developments taking place in networking are having significant impact on the traditional activities of librarians and information scientists, encouraging change in the pattern of existing information services and making possible new potentialities. For instance, the forms in which information is acquired, stored, manipulated and disseminated will be compelled to change as networked computing and information usage becomes more common in libraries and information centres. `Networking' is a somewhat complex term and requires to be viewed from a variety of perspectives in order to gain correct insight into its various benefits. The technical development of computer networking is concerned with the exchange of data rather than information. The concern of information professional is more with the transfer of information. This is certainly a challenging area for the effective use of networks for information systems. This Unit discusses information networking applications, with an emphasis on those issues important for librarians and information professionals.
11.2 BASIC CONCEPTS AND TERMINOLOGY As has been mentioned earlier, networking has emerged as a major breakthrough on several information related fronts over the last decade. To derive the various benefits of network developments, we need to understand what networks are and how they function, and with what objectives? To comprehend these aspects, it is necessary to understand some basic concepts and terminology associated with networking. Let us discuss some of them. 11.2.1 Network Definition "Whenever more than two units (e.g., persons, organisations, or computer terminals) are connected and share some attribute, a network is formed". This statement explains in a simple language the concept of a network. In other words, in an abstract sense, network means modes of interaction between people. However; there are three categories of networking which may be said to have considerable impact on information services. These are communication networks, computer networks and library and information networks. Let us discuss briefly each of these. 11.2.2 Communication Networks "A telecommunications network is a system consisting of communicating devices, such as terminals, an interconnecting media, such as cable, and a means of establishing communicating' , paths through the ,media between the communicating devices" (John feather, ed., 1997), In other words communications networks are made up of transmission lines, concentrators, switching mechanisms and non-data processing components. Networks cater for people with information intensive occupations. Specialised types of network have been developed in the last fifteen years or so, and new ideas are emerging almost daily. The main driving forces for these have been the arrival of compact, powerful and cheap technology and the need for business communications. 11.2.3 Computer Networks Computer networks are rather complex to identify. But, most of the definitions imply multiple
Public - this visually refers to entities that of networking or network services to any organisation or individual that whishes to subscribe. The telephone system is an example of a public network.
Information System and Networks
Cooperative -- this refers to networks that are supported and managed by their users. BITNET is an example of this type. Integrated Services Digital Network (ISDN) -- The development of public data networks for digital communications led to the existence of different networks for different purposes. This resulted in the duplication of networks. To avoid this, interconnection of two or more compatible or incompatible networks to form an intemet (network of networks) is attempted. The main aim of ISDN is to build a public network providing end-to-end digital connectivity which is capable of supporting a range of digital devices and services, both voice and non-voice, on the same basis. This allows users to send and receive data, text and image from computer systems as well as offering an enhanced telephone service. This is achieved over a single ISDN connection, so that one network can be used for all applications, providing higher speeds of transmission. Having known the different types of networks, let us now try to understand their objectives. 11 .3.1 Network Objectives The different types of networks that have been evolved share a set of common objectives. These include the following: Connectivity to permit different hardware and software products to be connected and communicate with each other; Simplicity to permit easy installation and operation of all network components; Modularity to enable building a wide variety of network devices from a relatively small set of mass-produced building blocks; Reliability to permit error free transmission by providing appropriate error detection and correction capabilities; Flexibility to permit the network to evolve as new needs arise or new technologies become available; Diversity of network services that can be easily used and yet isolate users from the technical details of network structure and implementation. While the above objectives may appear to be simple, their implementation is very complex since many tradeoffs are involved. Moreover, linking a variety of computing devices made by different manufactures requires hardware and software compatibility for seamless communication. A number of network architectures have been evolved to ensure this compatibility. Let us try to understand the meaning of network architecture and what it constitutes. Self Check Exercise
- List the common objectives of the different types of networks. Note: i) Write your answer in the space given below ii) Check your answer with the answers given at the end of this Unit. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… 11.3.2 Network Architecture A network architecture is the set of rules which govern the connection and interaction of the network components. A network architecture defines the protocols, message formats, and other standards to which communication hardware and N1ns/are must conform to achieve the network objectives computing devices complying with a given network architecture can intercommunicate. Communication between devices that conform to different network
architectures is possible only through complex gateways designed to translate the protocols between them.
Library and Information Networks
Some popular implementation of network architectures are: Xerox Network Systems (XNS) architecture. IBM's System Network Architecture (SNA), DEC's Digital Network Architecture (DNA), and the Department of Defense suite of protocols (TCP/IP). It may also be mentioned here that in 1978, the International Standards Organisation (ISO) recognised the importance for a standard for the exchange of information within and between networks and issued a , standard for standard network architecture. This is now becoming widely accepted and is in the form of a seven layer model known as the Open Systems Interconnection (OSI) Reference Model, The term `open' denotes the ability to transfer information between any two systems that conform to the reference model and its standards,
Apart from the basic concepts which we have discussed in the foregoing sections of this unit, there are two other important network parameters which need consideration. They are its topology and the transmission media used. The topology refers to the geometrical arr
angement and connection of the network nodes. The basic topologies are: i) point-to-point connection, ii) linear bus, iii) Ring connection, iv) star connection and v) multiconnected networks. Let us briefly discuss these.
Point-to-point connection: It has the advantage of simplifying routing decisions among nodes, but the reliability of the network depends on the reliability of the weakest links. Linear bus: In this type of network, all network nodes have unique addresses and are connected' to a common transmission medium. When a device transmits data on to the bus, it is received by all devices and is ignored, except by the one that is addressed. LANs based on the Ethernet use this type of topology. Ring Connection in which consecutive nodes are connected by point-to-point links arranged to from a closed path (ring). Information is passed from node to node around the ring until it arrives at the specific node that is addressed. Star Connection , in which all nodes are connected to a node called the central node or hub. The central node can be active or passive. If it is active, it is usually used to control the entire network and performs all the routing. This topology is used in applications where a central computer communicates with remote terminals or work stations. Multiconnected networks in which nodes are connected by point-to point links in an arbitrary fashion, with each node connected to at least two others. This improves reliability and reduces the likelihood of congestion, but makes routing much more complex since many paths are possible between any two nodes. The above discussed topologies are illustrated in the following diagram.
Library and Information 11.4 DEVELOPMENT OF LIBRARY NETWORKING Networks
There has not been an agreed set of definitions as to what the term 'network' means in the information sense (Kent and Galvin, 1979, p.19). The Oxford English Dictionary states that a network is "an interconnected chain or system of things", On the other hand the National Commission on Libraries and Information Science (NCLIS), U.S.A. defines network as two or more libraries and/or other organisations engaged in a common pattern of information exchange, through communications, for some functional purpose. A network usually consists of a formal agreement whereby materials, information and services provided by a variety of types of libraries and/or other organisations are made available to all potential users. Libraries may be in different jurisdictions but agree to serve one another on the same basis as each serves its own constituents. Computers and telecommunications may be among the tools used for facilitating communications among them" (ALA Year Book, 1976. p.248).
Yet another definition has been furnished by UNISIST II, Working Document which defined "Information Network' as "a set of interrelated information systems associated with institutional arrangements, in order to jointly implement information handling operation, with a view to pooling their resources and to offer better services to uses. They generally facie identical or Compatible procedures" (UNISIST II).
In the light of the definitions cited above Library and Information Networking is the area with a direct impact on information services, their efficiency and effectiveness. Definitions of Library Networks usually emphasis different levels of cooperation among libraries or other participating organisations in the network. According to Library of Congress (LC) the functions existing in library network are bibliographic utility and services centres. The main distinction between these functions is based on the product orientation of the bibliographic utility and the distributor orientation of the service centre. Service centres mainly function as access points to provide products and services obtained directly or derived from the bibliographic utilities. In addition to accessing the bibliographic utilities the service centres may also provide to the input data to the storage and retrieval facilities of bibliographic utilities.
It must be mentioned here that the broader world of information systems has grown over the last decade from a centralised model of terminal-based networks time-sharing a large computer, towards a decentralised view small autonomous cooperative systems linked in a complex open network on to a peer-to-peer basis. In library information networks also, a similar type of development has taken place owing to the technological advances providing nevpoami6litiee.
11.4.1 The Range of Network Services
The range of services provided by many resource sharing networks include storage and retrieval of data such as factual, physical and bibliographic data, document ordering and delivery services, general computer and support of group communication and decision making. The most widely used networks can be described by four major types of services. They are:
- shared cataloguing;
- • • • • • • on-line reference; shared circulation; Interlibrary loan.
Of course, cataloguing networks are by far popular type and are often cited as examples of computer applications to library services. Even though library network systems have undergone major development since 1960s and 1970s, the central objectives of networking remain-constant. They are:
To reveal the contents of large number of libraries, especially through accessibility of catalogue databases, using OPAC interfaces; To make resources shown in these catalogue databases available to individual libraries and user when and where they are needed; To share the expense and the work involved in creating catalogue database through the exchange of records and associated activities. additional functions that might be fulfilled by networks.
Information System and Networks
distribution and publication of electronic journals and other electronic documents; end-user access to other databases, such as those available on the online hosts and CD-ROM; value-added service such as electronic mail, directory services and file transfer; exchange of bibliographic and authority records usually in MARC format. If we follow closely the evolution of library networks, it will be observed that in the beginning, networks were established with limited and well-defined objectives. As the use of networking has become more pervasive due to the easy availability of' the infrastructure, the scope of the networks became broader and a number of interconnected consortia of networks and members has become possible. This has enabled the end-user to choose more than one route through the maze of networks in order to locate a given document or piece of bibliographic information. In other words, access barriers have become less and less. This has resulted in the establishment of key agencies in library networking. These key agencies may be grouped into two main categories. Large national libraries or centralised cataloguing services which create large bibliographic databases and also occasionally provide the document delivery facility; Cooperatives set up by groups of libraries, who feel that they and their users can profit by resource sharing through inter library loans and also by participation in the creation of a union catalogue. Self Check Exercise
- What are the central objectives of library networking? Note: i) Write your answer in the space given below ii) Check your answer with the answers given at the end of this Unit. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… 11.4.2 Library Networks in USA and UK The United States has definitely taken a lead in library networking. Among the prominent agencies in this regard, are the Library of Congress, and private agencies like Bibliographic Retrieval Services (BRS), National Medical Library (NLM), Systems Development Corporation (SDC), networks like OCLC (founded in 1971 as Ohio College Library Centre but now known as Online Computer Library Centre), WLN (originally Washington, but now Western Library Network), UTLAS (The University of Toronto Library Automation System) and RLIN (The Research Libraries Information Network) have played a major role in the development of library networking. Of the networks mentioned above, the OCLC (Online Computer Library Centre) is one of the largest of the bibliographic networks. Though, it is based in the USA, it has world wide library membership including Europe and Far East. OCLC possesses a very large database of MARC format data records and services a large number of libraries for production of their bibliographic (^) Y databases and for reference and interlibrary loan purposes. Through the late 1980s, OCLC responded to the changing conditions by a gradual opening of access to the existing systems by providing PC-based access rather than by specialised terminal only and by making access links from the Internet research network,; which many US academic libraries were beginning to use. This resulted in the establishment of _a new X.25 based network using capacity from the Sprint Commercial value-added network since 1991. The above development facilitated the introduction of network-to-network links, and the standardisation on X.25 rather than proprietary protocols permitted the building of direct links from local area networks thus increasing the connectivity for the user by allowing more flexible mode of connections.' Another development that has taken place during this period is that the need for any specialised OCLC hardware,-and the development of relevant software to suit it
Information System and Networks
11.4.3 Library and Information Networks in India
Till now you have learnt about the development of library and information networks in USA and UK. Let us now try to understand the developments taking place in India in this direction. The growth of library and information networks in India is of a recent origin. The growth can be traced to some of the policies that Government of India pursued during the last decade. For instance, the Technology Policy Statement (1983) realised the importance of Scientific and Technical Information (STI) and rightly emphasised the need for a technology information base. Also, in 1984, the Planning Commission Constituted a Working Group under the chairmanship of Dr. N. Seshagiri which recommended to the government the need for the modernisation of library services and informatics during the 7th plan period (1985 to 1990). In the same report, the Working Group recommended the interlinking of library systems in the country using modern information technology. The National Library and Information Policy document submitted in 1988 contained a recommendation to the effect that modem information technology must be used at national level to improve the library and information services in the country and make them more purposive and user-oriented. It is NISSAT (National Information System for Science and Technology) which took initiative for the establishment of CALIBNET in Calcutta and supported the formation of DELNET in 1988 and PUNET in Pune in 1992, ADINET in Ahmedabad in 1993, and BONET in Mumbai in 1994. In another effort INSDOC (Indian National Scientific Documentation Centre) Delhi took initiative and supported the formation of MALIBNET in Chennai in 1998. BALNET in Bangalore was registered as a society in 1997. The UGC did not lag behind in networking effort either. It established INFLIBNET in 1988 itself. INTLIBNET is a network of University and College Libraries. It became operational in 1991. It may be stated that though the above list is quite impressive on paper, some of the networks mentioned above have not yet become fully operational due to many limitations. In a way, technology is not being used in their operations and connectivity problems remains a problem apart from the lack of suitable hardware and software and manpower. Also, there appears to be no coordination among these networks resulting in duplication of efforts. The objectives, functions and the comparative aspects of the performance of the above mentioned networks will be discussed in Unit 12 of this course (Course-7, Block-4) as such, it is not attempted here. It may be important to refer here to the Report of the Working Group of the Planning Commission on Libraries and Informatics for the Ninth Five Year Plan (1997-2002). This report was prepared under the chairmanship of Shri B.P. Singh, the then Secretary, Department of Culture. This document is a significant one in the sense that it is comprehensive and contains recommendations of far reaching consequence, if implemented fully. It has a large number of recommendations (17) on the modernisation as well networking of libraries including public libraries. 11.4.4 Non-Bibliographic Data Networks in India In the previous section of this unit, you have been exposed to some of the library and ,information networks in India. We will now briefly discuss some of the significant data communication networks functioning in the country. The National Informatics Centre (NIC) was established in 1975. One of its objectives was to build intra-city and inter-city computer networks for interconnecting various ministries/ departments of the central government and autonomous organisations for a distributed governmental information system". To fulfill this objective, the NIC established NICNET in 1977. It links regional nodes at Delhi, Pune, Bhuwaneswar and Hyderabad and 32 nodes at state and union territory levels and 439 nodes at district headquarters. NICNET is based on spread spectrum multiple access technique and uses C-2000 series of micro-earth stations NICNET has created a number of databases and networking. Many information systems have been designed and established by NIC for the purposes providing administrative information support for the efficient functioning and management of the central government. All these databases can be accessed through NICNET. NICNET -also provides the facility for the transmission of bibliographic data. Another effort in this direction is the establishment of INDONET. INDONET is an integrated information management and distributed data processing facility. It is a commercial network with nodes at Calcutta, Bombay and Madras (Chennai) on IBM 4361. It is connected to cities
like Ahmedabad, Bangalore, Delhi and Pune through MUXs/lcluster controllers. INDUNBT use IBM's System Network Architecture (8NA). It is planned as a geographically dispersed computer network linking scattered organisations in the country.
Library and Information Networks
VIKRAM is yet another public data network established by the Department of Telecommunications. If is a packet switched data network having its management centre at Delhi and switching nodes at Bombay (Mumbai), Calcutta (Kolkata). Madras (Chennai), Bangalore, Hyderabad, Ahmedabad und pune with 12 remote access points all connected by leased or dialup lines.
The Department of Electronics established ERNET mail during the Seventh Plan (1986-1991) to provide academic and research institutions with electronic mail facilities. It is used by many academic and research institutions.
There are other similar efforts in this direction but the Gateway Packet Switching System (GPSS) is of the significant moves. The GP3Sestablished Packet Assembler- Dissemblers (PADs) in Delhi, Madras (Chennai),Bangalore, Hyderabad and Pune. Network's like NICNET, IND0DET and VIKRAM are connected to -this gateway.
Self Check Exercise
l) What is subject representation?
Note: i) Write your answer in the space given below
ii) Check your answer with the answers given at the end of this Unit.
………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… …………………………………………………………………………………
11.5 SUMMARMY
In this Unit, an effort has been made to explain to you in simple terms the concept of networks and networking. Networking is complex term and requires to be viewed from a variety of perspectives in order to gain insight into its different facets. To enable you to fully grasp what constitutes networking and why it is needed, some significant technical terms and concepts relating to the field have been explained in this Unit.
The categories and types of networks have been briefly described to provide you with background information, Basic aspects like 'network objectives', 'network architecture', 'network topology' and 'transmission media' have been discussed to provide exposure to the technology underlying the functioning of networks. The reasons for the proliferation of networks and their application especially in the field of information dissemination have been briefly mentioned. The development of library and information networks in developed countries like USA and UK has been described to expose you to the World scenario.
The Unit concludes with the discussion of efforts made in India for developing Library and Information Networks along with a brief account of sonic of the significant data communications furnished networks and their connectivity facilities, To facilitate you with learning process and to enable you to acquire basic knowledge, self check exercises, as also model answers to them along with explanations to some of the technical terms - in the form of key words have also been furnished .All these feature would aid you in comprehending the concept of networks and networking and their impact in the provision of information services in an effective manner.
11.6 ANSWERS TO SELF CHECK EXERCISES
- In the abstract sense the term 'network' means modes of interaction between people. We can also define the term network by saying that a network is formed when two or more units (i.e., persons, organisations, or computer terminals) are - connected and share some attributes.
Library and Information 11.7 KEY WORDS Networks
Bridge: A hardware device for interconnecting local area networks (LANs) of the same type.
Broadband Networks: A high-speed capacity integrated network appropriates for multi-media information networking.
Bulletin Boards: An electronic notice board for posting and retrieval of message, which can be accessed by a user community.
Connectivity: The ability to interconnect computer systems and networks for the exchange of information.
EDI Electronic Data Interchange: The use of structured messages for the generation, exchange, and processing of standard business type documents.
EDIFACT: An international standard for electronic data interchange
Ethernet: A widely used type of local area network which uses a bus topology to broadcast messages to all connected nodes.
Facsimile: A hardware device for the transmission and receipt of documents in image format: the Group III fax format standard is most widely used, supplemented by the higher quality Group IV standard.
FTP File Transfer Protocol: A protocol for access to and transfer of data files in a TCP/ IP-based network.
FTAM File Transfer and Access Method: An OSI application layer protocol for access to and transfer of data files between different computer systems.
Gateway: A link between one computer network and another, which allows messages to pass between them. A gateway service may offer access to several networks through a single point.
Image Format:. Information represented as dot patterns. (bit maps), created by scanning a printed page, digitising images, or through a fax machine.
Information Network: A network for the exchange of information often via one or more computer networks between human participants.
Interlibrary Loan Protocol: An OSI application layer protocol for the exchange of interlibrary loan messages between automated library systems.
Internet: A global scale network of networks.
ISDN: Integrated Service Digital Network: An integrated network designed for both digital voice and data, founded on the existing telephone network.
JANET: The Joint Academic Network, which links the higher education institutions in U.K.
Kbps: Kilobits per second I kbps = 1,000 bits per second
Kilostream: A BT leased line providing data rates from 64 kbps to I mbps.
Leased Lines: Point-to-point data circuits, provided by telecommunications operators, which can be rented for private use by larger organisations.
Local Area Networks: Computer networks which are limited in geographical extent and number of connections, to a small site.
Mbps: Megabits per second I Mbps = I million bits per second,
Message Transfer Agent: An element with in the X:400 electronic mail interchange standard which deals with routing and forwarding messages between points on the network.
Node: An end-point on a computer network, one of the computer systems which it connects.
OCLC (Online Computer Library Centre): A large US-based bibliographic utility active in library networking.
Open Systems Interconnection (OSI): The ability to inter-connect computer systems based on use of a basic reference model which modularises the communications process into seven functional layers, incorporating existing network standards and developing new ones.
Information System and Networks
Open Document Architecture (ODA): A format standard for document interchange between different document processing systems, based on a logical analysis of document structures Optical Fibre: A transmission medium consisting of a very fine glass fibre alone on which data is transmitted. A cable consists of many fibres bundled together. Packet Switching : A method of transmitting data which divides a message into discrete packets each of which is routed through the network independently. PAD (Packet Assembler/Disassemble): A network device for creating packets from a message for transmission and reassembling their, in correct order at the destination point. PDN (Public Data Network): A packet switched data network for public use provided by a network operator and normally using X: 25 standards. Protocols: A set of fixed rules governing the procedures of transmission of computer data used by all computer systems within a network as a common communications language'. **Router:** A hardware device for interconnecting networks of different types, and routing messages onwards to their destination. **Search and Retrieve:** An OSI application layer protocol for information retrieval similar to Z 3900. **Server:** A node on a network which provides a particular service for other nodes for example access to files or database records, (^) - management of mail messages, print services. A server node is accessed through a client node. **Store and Forward:** A. wide area network (WAN) technology to buildmultistage' networks in which each node can store data as it is received and forward it to the next node along the route when possible. Systems Network Architecture: A proprietary closed set of protocols for internetworking IBM systems. TCP/IP (Transmission Control Protocol/Internet Protocol): An `Open' set of network protocols, used in the Internet and elsewhere, which rival the OSI model. Telecommunications Networks: Wide area networks (WRNS) developed as public utility by network suppliers, for telephone, computer data and integrated services. Terminal Networks: A computer network built in star topology, in which many terminals are connected to a central computer system. Text Format: Information represented as alphanumeric characters by some binary coding scheme, such as ASCII. User Agent: An element of the X 400 electronic mail interchange standard which acts as the interface between the local mail system and the message transfer system. Wide Area Networks (WANs): Computer networks, which extend over a wide geographic area in which constituent nodes relay information from source to destination. Work-station: A powerful desktop computer which provides high quality graphical screens and substantial processing abilities. X.25: A get of lower level (physical, data link, and network layer) protocols approved by the CCITT, widely used for telecommunication networks. X 400: An OSI application layer standard for the interchange of mail messages between different electroni6 mail systems. Z 39.50: A protocol for information retrieval approved as a US standard and similar to the OSI Search and Retrieve protocol.
11.8 REFERENCES AND FURTHER READING Harries, Steve (1993). Networking and Telecommunications for Information Systems, London: Library Association Publishing.
