Search (48 results, page 2 of 3)

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Abstract

Details the elements of the ISO Reference Model for Open Distributed Processing. Explores the challenges facing in from multimedia and stream communication

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Abstract

Adaptive, in-call, bandwidth reservation may be used to enhance bandwidth utilization in a policed asynchronous transfer mode (ATM) virtual path shared by traffic streams originated by many bursty sources. Presents a model, based on Markov-modulated sources and stochastic fluid methods, for performance analysis of the proposed mechanism. The model, corroborated by simulations, is used to study achievable bandwidth gain and the effects of feedback delay and competing reservation processes

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Abstract

Examines a number of possible OSI system implementation strategies based on the various prevailing system facilities: processes, threads, kernel and front-end processors. Analyzes the pros and cons of the strategies showing their relative merits in implementation. The analysis leads to the recommendation of an enhanced subsystem architecture that holds the best compromise of the conflicting requirements of modularity and efficiency

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Abstract

The Z39.50 standard for information retrieval is important from a number of perspectives. While still not widely known within the computer networking community, it is a mature standard that represents the culmination of two decades of thinking and debate about how information retrieval functions can be modeled, standardized, and implemented in a distributed systems environment. And - importantly -- it has been tested through substantial deployment experience. Z39.50 is one of the few examples we have to date of a protocol that actually goes beyond codifying mechanism and moves into the area of standardizing shared semantic knowledge. The extent to which this should be a goal of the protocol has been an ongoing source of controversy and tension within the developer community, and differing views on this issue can be seen both in the standard itself and the way that it is used in practice. Given the growing emphasis on issues such as "semantic interoperability" as part of the research agenda for digital libraries (see Clifford A. Lynch and Hector Garcia-Molina. Interoperability, Scaling, and the Digital Libraries Research Agenda, Report on the May 18-19, 1995 IITA Libraries Workshop, <http://www- diglib.stanford.edu/diglib/pub/reports/iita-dlw/main.html>), the insights gained by the Z39.50 community into the complex interactions among various definitions of semantics and interoperability are particularly relevant. The development process for the Z39.50 standard is also of interest in its own right. Its history, dating back to the 1970s, spans a period that saw the eclipse of formal standards-making agencies by groups such as the Internet Engineering Task Force (IETF) and informal standards development consortia. Moreover, in order to achieve meaningful implementation, Z39.50 had to move beyond its origins in the OSI debacle of the 1980s. Z39.50 has also been, to some extent, a victim of its own success -- or at least promise. Recent versions of the standard are highly extensible, and the consensus process of standards development has made it hospitable to an ever-growing set of new communities and requirements. As this process of extension has proceeded, it has become ever less clear what the appropriate scope and boundaries of the protocol should be, and what expectations one should have of practical interoperability among implementations of the standard. Z39.50 thus offers an excellent case study of the problems involved in managing the evolution of a standard over time. It may well offer useful lessons for the future of other standards such as HTTP and HTML, which seem to be facing some of the same issues.
This paper, which will appear in two parts, starting with this issue of D-Lib, looks at several strategic issues surrounding Z39.50. After a relatively brief overview of the function and history of the protocol, I will examine some of the competing visions of the protocol's role, with emphasis on issues of interoperability and the incorporation of semantics. The second installment of the paper will look at questions related to the management of the standard and the standards development process, with emphasis on the scope of the protocol and how that relates back again to interoperability questions. The paper concludes with a discussion of the adoption and deployment of the standard, its relationship to other standards, and some speculations on future directions for the protocol. This paper is not intended to be a tutorial on the details of how current or past versions of Z39.50 work. These technical details are covered not only in the standard itself (which can admittedly be rather difficult reading) but also in an array of tutorial and review papers (see <http://lcweb.loc.gov/z3950/agency> for bibliographies and pointers to on-line information on Z39.50). Instead, the paper's focus is on how and why Z39.50 developed the way it did, and the conceptual debates that have influenced its evolution and use. While a detailed technical knowledge of the operation of Z39.50 is certainly helpful, it should not be necessary in order to follow most of the material here. Some disclaimers are in order. I have been actively involved in the development of Z39.50 since the early 1980s and have been a participant -- and on occasion, even an instigator -- of some of the activities described here. This paper is an attempt to make a critical assessment of the current state of Z39.50 and a review of its development with the full benefit of hindsight. It recounts a number of debates that occurred within the developer community over the past years. In many of these, I advocated specific positions or approaches, sometimes successfully and sometimes unsuccessfully. What is presented here is one person's perspective - mine --, which is sometimes at odds with the current consensus with the developer community; I've tried to represent opposing views fairly, and to differentiate my opinions from fact or consensus. However, others will undoubtedly disagree with many of the comments here.

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Abstract

This article will examine the Z39.50 Information Retrieval protocol. It will look at some of the history of the protocol, its operation, and some of the major projects that have made use of it. There has been enough written (perhaps too much) about Z39.50 in the last several years so it is not intended to be a tutorial or detailed description of the protocol. The material that will be presented will try and put some context around the discussion. For those readers who are interested in delving into Z39.50 in a more technical manner, references to much of the material that has been written about it over the years will be provided at the end. Finally, the article will conclude with some thoughts on how technology and technological infrastructure have changed in the years since Z39.50 was initially developed and deployed, and where the protocol has so far lived up to its goals, and where it has perhaps failed to meet some of the high expectations that at least some people involved in the Z39.50 community held for it. The article will conclude with some of the author's speculations (and they are really no more than that) of what the future role of Z39.50 is likely to be.

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Abstract

This study aimed to determine if the searching behaviour of remote users of LIAS, Penn State's online catalogue differed from those using the OPAC within the library. More than 1.000 searches done by remote users (those accessing the system via either dial-access or the university's computer network) were compared to more than 1.000 searches done by in-house users. Each search was duplicated step by step and analysed according to a pre-determined set of criteria. Although few dramatic differences were found between the 2 groups, there were enough subtle differences to generate interest. In general, remote users are the more sophisticated searchers, bearing out the assumption that remote users seem to have a better conceptual knowledge of how an information system should operate. On the other hand, they struggle more with the procedural details of how to use the OPAC. Dial-access users seem to constitute a unique group of users: their searches are often quite different than those done by either network or in-house users

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Abstract

Describes SUNET, the Swedish University Network, a medium speed network connecting most most mainframe and smaller computers in Swedish universities. Discusses the application of SUNET to remote access to OPACs

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Abstract

A special issue devoted to the international telecommunications environment and the new institutional arrangements for the regulation of international telecommunications as well as in standards setting procedures

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Footnote

Rez. in: Library Association Record 95(1993) no.2, S.113 (D. Byrne)

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Abstract

Hinich and Molyneux review the literature of internet measurement and note three results consistently to be found in network traffic studies. These are "self-similarity," "long-range dependence," by which is meant that events in one time are correlated with events in a previous time and remain so through longer time periods than expected, and "heavy tails" by which they mean many small connections with low byte counts and a few long connections with large byte counts. The literature also suggests that conventional time series analysis is not helpful for network analysis. Using a single day's traffic at the Berkeley National Labs web server, cumulated TCP flows were collected, log transforms were used with the adding of .01 to all values allowing log transforms of the zero values, and providing a distribution that overcomes the heavy tail problem. However, Hinich's bicorrelation test for nonlinearity using overlapping moving windows found strong evidence of nonlinear structures. Time series analysis assumes linear systems theory and thus additivity and scalability. Spectral analysis should provide large peaks at the lowest frequencies if long range dependence is present since the power spectrum would go to infinity if the frequency goes to zero. This does not occur and so long range dependence must be questioned, at least until it is determined what effect other OSI layers may have on the TCP data.

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Abstract

Examined two groups of online catalogue users segregated by their method of access to the system: terminals in the library or remote workstations. An online survey collected demographic data, perceptions on source and terminal accessibility, and information on usage, task variety and search satisfaction. Transaction logs furnished data on browsing behavious, while interviews of both groups provided additional information about remote use. Results indicate that remote use is comparable to traditional use

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Abstract

Discusses the advantages and disadvantages of a common user interface to enable searching of all databases regardless of producer, supplier or location, such as local CD-ROM, or network. Explains client server architecture, the basic component of a common user interface and outlines current developments including the Z39.50 application layer protocol. A common user interface will result in greater synergy between information providers, technology providers, distributors and information professionals. It will also be able to search across the Internet and make that huge wealth of data much more available than it currently is. Predicts that a common user interface will be in operation by the turn of the century

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Abstract

Describes the development of SuperJANET, the new optical fibre network for the UK academic and research community. Considers pilot applications for SuperJANET covering library and non library applications and strategic issues to be met for SuperJANET to become an information superhighway. Gigabyte networks will be 1.000 time faster than JANET and will enable sophisticated image and voice communication. SuperJANET uses synchronous digital hierarchy technology. SuperJANET is being developed and and introduced in a number of phases. Discusses supercomputing, library and information services, and strategic issues. Examines the role of technology and librarians in the development of the virtual library

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Abstract

Discusses Austrian government policy on the information superhighway (ISH) since Aug. 94. The Austrian telecommunications infrastructure is far behind the standards of Europe. The Austrain PTT monopoly over the public telecommunications network is an obstacle to development. The rates for data services are still based on copper cable with transmission speeds of 9600 Kbps. Although there are various ISH initiatives in Austria, the gap between vision and reality is large. Describes the initiatives of the Austrian National Host and the Bureau for International Research and Technology Cooperation; the Austrian Platform for Telematic Applications; BNet (Burgenland); Telematik Initiative Wien; TELKIS Telekommunikationsinitiative Steiermark; Datahighway Upper Austria; Vorarlberger Telekommunikations GmbH; Telematik Initiative; Datenbahn Telecom GmbH (Salzburg); Ti-KOM (Tirol) and other initiatives

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Abstract

The ANSI Z39.50 standard was adopted 10 years ago. It outlines a set of rules and procedures to allow a computer system to search the databases provided by another system and to retrieve the results of that search. Traces its development adoption in library automation product lines. Recent major developments have been the migration to version 3 and the adoption of community profiles. Community profiles are documents that describe agreements that a community of interest develops to ensure clients and servers can interpret in specific ways. Describes the Government Information Locators Service, WAIS, ATS, ZDSR, Cataloguing, CEOS CIP, Digital Collection, Digital Library Objects and Museum Profiles

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Abstract

This report presents the results of a survey of users who access the University of California's online union catalog, the MELVYL library system, via microcomputers with modems or connections carried through local or wide area networks. The report includes descriptive statistics on user location, status, subject interest, affiliation, in-library versus out-of-library usage patterns, need for assistance, and desire for new features

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Abstract

OPACs in an increasing number of libraries are now available using the Joint Academic Network (JANET). Access has tended to be obstructed, for the casual user, by the lengthy JANET addressing codes and varying log-on procedures required by each library system. Discribed how a communications and menu package on an IBK/PC can be used so that by merely pressing cursor control, return and escape keays, any user can gain access to any one of over 40 OPACs linked to JANET

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Source

Advances in library resource sharing. 2(1991), S.146-150

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Abstract

'Remote control' programs allow users to dial into and use a PC from a location away from their office. Examines what is involved in setting up a PC as a 'mini host' and introduces a freeware remote control program to get started. Discusses the PC as a host; commercial products; the PC remote utility and how to use it; configuring the host and the caller and remote booting

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Abstract

Networks allow different users from outside the library to have remote access to library catalogues. These remote users may face problems that differ from the OPAC users' in the library. They may not be comfortable with the computer technology and may not be familiar with the OPAC of the library. Libraries should offer different support services from those provided to on-site users. These users need technical advice as well as special instruction aids and guides to lead them to the information they want to retrieve