Computer Networks (1976)最新文献

Some practical suggestions are made as to how data abstraction may be used to provide a modular framework for the design of open systems and their means of interconnection. This framework is technically advantageous in clarifying the interfaces between the parts of a large design, and would also help in planning and coordinating the work of standards committees.

A reference model for languages applicable to local system function is compared with the reference model for open systems interconnection (OSI), and a clarification is suggested which would make the models compatible. Two major functional requirements are proposed for the application layer of the OSI model, namely the ability to transmit arbitrary operations to be performed on remote objects, and the option to specify whether objects or merely references to them should be transmitted.

SIRIUS-DELTA is a distributed database system which is aimed at co-operation of heterogeneous local database systems. It illustrates how the Open Systems approach has been used in the context of distributed database systems, mainly in its architecture and its Data Manipulation Protocol. It also illustrates that distributed databases is an area where co-operation between ISO/TC97/SC5 Programming Languages and ISO/TC97/SC16 Open Systems Interconnection sub-committees is of a major importance for future developments.

Network and relational database standards are under development by technical committee X3H2 of the American National Standards Institute. This paper is an overview of the procedure language interface to these proposed standards. It introduces the basic structures and operations of each data model, focuses on the procedure language interface as a facility for database access from external languages, and discusses various alternatives for use of the database language standard with existing standard programming languages. The paper contains example application programs of each access alternative and concludes with a discussion of basic requirements for application of the standard specifications to distributed database processing in an open systems environment.

Application programs access Open System Interconnection services through a Programmatic Interface. This Programmatic Interface should be made available to users of high level languages most commonly used for programming applications. This paper presents a Cobol oriented programmatic interface giving access to the Presentation Virtual Terminal Services of CII-HB and HIS Distributed Systems Architecture, DSA, which is built in accordance with ISO reference model for OSI. The virtual terminal model used is described in terms of presentation objects and their attributes, as well as the operations performed on these objects. A correspondance is given between this model and the COBOL communication model.

The aim of this paper is to present a FORTRAN interface to the communication software developed by CREI for experimental purposes in a large mainframe, connected to Euronet.

The paper first describes the environment in which the interface was designed; then details of the primitives are given. A survey of the local management problems related to this interface follows, together with the features inserted to ensure an easy and reliable use, even by unexperienced programmers.

The success of standard protocols for the transfer of files depends on the existence of a commonly agreed set of concepts relating to files. This raises issues for standardization outside the protocols area, and potentially affects many aspects of information processing standardization. The solution currently being developed is based on a model of the resource called a Virtual Filestore. The model making activities necessary to ensure a common conceptual framework are discussed, and the role of this model in the process of defining communication service and protocol standards established. The components of the virtual filestore are outlined and their relationship to future work on languages and related standards explained.

This paper explores the impact of Open Systems Interconnection (OSI) upon programs and programming and proposes two interfaces to the reference model of value to the applications programmer. In addition, it considers the impact of OSI upon Operating System Command and Response Languages and comments on the affinity between these and the intercommunication requirements for Job Transfer and Manipulation in a distributed environment. Because of the value of abstract data typing as a formal method of describing matters of concern to the Application and Presentation layers, the paper recommends close liaison between those developing high level protocols and those defining languages which exhibit strong data typing.

ALIS (Automated Library Information System) comprises a catalogue search system combined with a circulation control system with bar-code readers. The catalogue search part of ALIS makes it possible for the user via VDU's or typewriter terminals to search for literature in DTB's data base using as search criteria author names, keywords in titles, UDC numbers (Universal Decimal Classification System), ISBN, ISSN, CODEN, language codes, year of publication or combinations of these.

In consequence of the combination of the search system and the circulation control system the user may obtain not only the bibliographic records for the retrieved documents but also information about their immediate status (“on shelf”, “on loan”, “on reservation” etc.).

The bibliographic data base of ALIS, with more than 125,000 bibliographic records, is placed at a service centre in Copenhagen (Datacentralen af 1959) and the circulation control part of ALIS is placed in a minicomputer in DTB. The search system is based on STAIRS/CICS, but the minicomputer enables the user to choose between the English STAIRS dialogue and the Danish dialogue with extended commands and ordering facilities.

The system is accessible by direct call or via EURONET, SCANNET or DTH-net (the local university network).