Different Classes Of Users Research Articles

The rationale of the current optical networking initiatives

The future of networking is to move to an entirely optical infrastructure. Several leading National Research Networking organizations are creating test-beds to pilot the new paradigm. This paper explores some thoughts about the different usage models of optical networks. Different classes of users are identified. The services, required by the Internet traffic from those different classes of users, are analysed and a differentiated Internet architecture is proposed to minimize the cost per transported packet for the whole architecture.

A hierarchical access control model for video database systems

Content-based video database access control is becoming very important, but it depends on the progresses of the following related research issues: (a) efficient video analysis for supporting semantic visual concept representation; (b) effective video database indexing structure; (c) the development of suitable video database models; and (d) the development of access control models tailored to the characteristics of video data. In this paper, we propose a novel approach to support multilevel access control in video databases. Our access control technique combines a video database indexing mechanism with a hierarchical organization of visual concepts (i.e., video database indexing units), so that different classes of users can access different video elements or even the same video element with different quality levels according to their permissions. These video elements, which, in our access control mechanism, are used for specifying the authorization objects, can be a semantic cluster, a subcluster, a video scene, a video shot, a video frame, or even a salient object (i.e., region of interest). In the paper, we first introduce our techniques for obtaining these multilevel video access units. We also propose a hierarchical video database indexing technique to support our multilevel video access control mechanism. Then, we present an innovative access control model which is able to support flexible multilevel access control to video elements. Moreover, the application of our multilevel video database modeling, representation, and indexing for MPEG-7 is discussed.

On the radio capacity of tdma and cdma for broadband wireless packet communications

Studies of the capacity of cellular systems, stated in terms of the admissible number of remote users, have generally been limited to voice telephony. We address the problem of comparing the interference-limited performance of code-division multiple-access (CDMA) and time-division multiple-access (TDMA) systems in a packet-switched environment. The objective is to determine whether the capacity advantages claimed for circuit-switched CDMA still apply in a packet-switched environment, where the natural time diversity of bursty transmission may be a significant factor. Under a set of specific assumptions about the wireless environment (including path loss, shadow fading, multipath delay spread, cochannel interference, power control, and coding), we evaluate the number of users that can be admitted to the system while maintaining some desired quality-of-service (QoS) level. Four different classes of users with different characteristics and requirements are considered. The system capacity is found to depend significantly on the QoS objectives, which might be stated in terms of availability of some specified signal-to-interference level, packet-loss rate, or mean tolerable delay. The main finding is that strict requirements imposed on the radio access level tend to favor CDMA, whereas if some form of packet recovery is allowed at the higher layers (implying a relaxed set of requirements on the radio interface), then a somewhat higher capacity may be achieved by TDMA.

A Stackelberg Network Game with a Large Number of Followers

We consider a hierarchical network game with multiple links, a single service provider, and a large number of users with multiple classes, where different classes of users enter the network and exit it at different nodes. Each user is charged by the service provider a fixed price per unit of bandwidth used on each link in its route, and chooses the level of its flow by maximizing an objective function that shows a tradeoff between the disutility of the payment to the service provider and congestion cost on the link the user uses, and the utility of its flow. The service provider, on the other hand, wishes to maximize the total revenue it collects. We formulate this problem as a leader-follower (Stackelberg) game, with a single leader (the service provider, who sets the price) and a large number of Nash followers (the users, who decide on their flow rates). We show that the game admits a unique equilibrium, and obtain the solution in analytic form. A detailed study of the limiting case where the number of followers is large reveals a number of interesting and intuitive properties of the equilibrium, and answers the question of whether and when the service provider has the incentive to add additional capacity to the network in response to an increase in the number of users on a particular link.

An importance sampling algorithm for the simulation of a GPS scheduler

AbstractA key requirement of modern telecommunications networks is the capability of providing a variety of Quality of Service (QoS) guarantees to different classes of users. In this scenario scheduling systems play a major role, thanks to their ability of offering different levels of service, while preventing some “greedy users” from degrading the QoS of other classes. A primary QoS parameter is the Cell Loss Probability (CLP), whose typical values are very small and therefore difficult to estimate through standard Monte Carlo (MC) simulation, since long run times are required to achieve accurate results. Under proper conditions, Importance Sampling (IS) techniques can speed up simulations involving rare events. In this paper we propose an application of IS to the simulation of a Generalized Processor Sharing (GPS) scheduler, fed by Markov Arrival Processes (MAP). The algorithms we propose are based on large deviations principles, which provide asymptotic results on the decay rate of per‐session queue length tail distributions in an idealized GPS discipline. In particular, we first present a scheme for the simulation of a two‐buffer system, then we extend the technique to the general case of a multi‐buffer scheduler. We subsequently employ our algorithms to simulate a packetized realistic system, namely the Packet‐by‐packet Generalized Processor Sharing.

A HIERARCHICAL NETWORK GAME WITH A LARGE NUMBER OF PLAYERS

We consider a hierarchical network game with multiple links, a single service provider, and a large number of users with multiple classes, where different classes of users enter the network and exit it at different nodes. Each user is charged by the service provider a fixed price per unit of bandwidth used on each link in its route, and chooses the level of its flow by maximizing an objective function that shows a trade-off between the disutility of the payment to the service provider and congestion cost on the link the user uses, and the utility of its flow. The service provider, on the other hand, wishes to maximize the total revenue it collects. We formulate this problem as a leader-follower (Stackelberg) game, with a single leader (the service provider, who sets the price) and a large number of Nash followers (the users, who decide on their flow rates). We show that the game admits a unique equilibrium, and obtain the solution in analytic form. A detailed study of the limiting case where the number of followers is large reveals a number of interesting and intuitive properties of the equilibrium, and answers the question of whether and when the service provider has the incentive to add additional capacity to the network in response to an increase in the number of users on a particular link.

Interference control and chip waveform design in multirate DS-CDMA communication systems

We study the interference effects in a multirate DS-code-division multiple-access (CDMA) system. Optimum chip waveform selection with arbitrary shapes is analyzed using a time domain approach. The problem is posed as an interference minimization problem under energy and time-bandwidth constraints and prolate spheroidal wave functions are used to arrive at a solution. Various factors affecting the interference are identified and the trade-off between competing factors is analyzed. The effect of the interchip interference on the optimum chip waveform design is also quantified under a practical bandwidth constraint. We study the benefits of employing two different chip waveforms for two classes of users. We compare the performance of systems employing two different chip waveforms with that of a single-chip waveform system such as IS-95. We show that when the power imbalance is large, it is advantageous to employ two different chip waveforms for different classes of users.

The Rural-Urban 'Digital Divide' in New Zealand: Fact or Fable?

Much electronic commerce literature addresses the potential existence of digital divides between different classes of users. While many studies document users reported perceptions of disadvantage or cite infrastructure availability benchmarks, few studies quantify the extent of such divides in actual uptake and usage of electronic communications tools. This study seeks to quantify the extent of perceived rural-urban digital divides among businesses in New Zealand. Yellow Pages business register data are analysed to determine business uptake of e-mail and websites by location. The results challenge conventional perceptions of disadvantage on the basis of geography alone. Indeed, some provincial areas demonstrate higher uptake of business e-mail than their urban counterparts. Smaller and more remote provincial centre businesses are more likely to be using e-mail than their counterparts closer to the metropolitan centres. Those centres most remote from New Zealand's traditional commercial centre demonstrate higher uptake than those closer. Explanations based upon disadvantages such as poor telephony infrastructure appear inadequate in accounting for these observations. Rather, we contend that while infrastructure may play some part in the explanation for low rural hinterland uptake, the results of this study are consistent with economic determinations of the optimal time to invest in new technologies. Specifically, higher provincial and rural communication costs are a significant factor in encouraging higher and earlier levels of provincial and rural e-mail adoption, and the optimal time to invest in website adoption depends more upon firm size, local economic conditions and product than infrastructure quality and business location.

Cellular multicode CDMA capacity for integrated (voice and data) services

This paper analyzes the capacity of a multicode direct sequence-code division multiple access (DS-CDMA) cellular architecture supporting integrated (voice and data) traffic. The capacity estimate (on the uplink) is the number of voice users and data users, at different data rates, that the system can support with quality-of-service (QoS) guarantees (frame error rates (FER), outage probability). This estimate is based on an interference analysis that considers both perfect and imperfect power control, different user distributions in the cell, and the coverage trade-off resulting from hand-set power limitations. Localized interference from high speed data (HSD) users, combined with the effects of power control, adversely impacts voice capacity. The analysis investigates the effect of two important factors on capacity: (1) received power levels for the different classes of users and (2) data user activity. The results obtained are useful in designing power allocation and burst-level admission control strategies to optimize the capacity.

Web server support for tiered services

The evolving needs of conducting commerce using the Internet requires more than just network quality of service mechanisms for differentiated services. Empirical evidence suggests that overloaded servers can have significant impact on user perceived response times. Furthermore, FIFO scheduling done by servers can eliminate any QoS improvements made by network-differentiated services. Consequently, server QoS is a key component in delivering end to end predictable, stable, and tiered services to end users. This article describes our research and results for WebQoS, an architecture for supporting server QoS. We demonstrate that through classification, admission control, and scheduling, we can support distinct performance levels for different classes of users and maintain predictable performance even when the server is subjected to a client request rate that is several times greater than the server's maximum processing rate.

Java access to numerical libraries

SUMMARY It is a common and somewhat erroneous belief that Java will always be ‘too slow’ for scientific computing. Two projects under way at the University of Tennessee are addressing the question of scientific computing via Java: NetSolve and f2j. The approaches taken by these two projects are radically different. NetSolve allows users to access pre-installed computational resources, such as hardware and software, distributed across the network. Using these resources, the user can easily perform scientific computing tasks without having any computing resource installed on his or her computer. NetSolve features a Graphical User Interface written in Java as well as a Java Application Programming Interface. The f2j (Fortran to Java) project will provide the numerical subroutines translated from their Fortran source into class files suitable for use by Java programmers. This makes it possible for a Java application or applet to use established legacy numerical code that was originally written in Fortran. This article describes the research issues involved in these two projects and their current limitations. We also explain how, although using two different paradigms and addressing somewhat different classes of users and applications, NetSolve and f2j achieve a common goal: to provide efficient, reliable and portable access to standard numerical libraries via Java. ©1997 John Wiley & Sons, Ltd.

Integrated systems II: Multi-tier interfaces for integrating families of systems

Of critical importance is the design of the man-machine interfaces for general rule based systems. They must serve (i) as user-friendly interfaces for different classes of users for different applications and (ii) to invoke service components in integrated packages without interrogating users. These objectives are achieved with a multitier interface design whose two parts, the Interactive User-Friendly Interface (IUFI) and the System Interface (SI), communicate with each other via commonly used notational systems and can be invoked independently of each other. The user-friendly interface, which is uniquely designed for each user discipline, passes information to the SI. The SI does not change for new IUFI designs and it can be invoked by other rule based systems without interrogating users.

An approach for building an integrated environment for molecular biology databases

The requirements of a traditional integration of databases include hiding the heterogeneity among its member databases, preserving their autonomy, supporting controlled data sharing, and providing a user-friendly interface, with a performance comparable to that of a homogeneous distributed database system. In this paper, we describe a variation of the loosely coupled federated database approach that satisfies these requirements and is specifically oriented toward the special characteristics and needs of molecular biology databases. The approach differs from the traditional federated database approach in that it also integrates software tools together with the databases. In addition, the system gives the graphical user interface a more central role in the integration. Thus, the system has all the advantages provided by a visual user environment and is thus more user-friendly than traditional linguistic approaches. The paper also includes a description of XBio, a system which constructs such an integration. The design of XBio ensures robustness and can be customized to the needs of different classes of users.

IT Security and Integrity

Data security implies the avoidance of theft, loss or unauthorised disclosure of data. This may have financial implications either because the lost can be converted into money by the person who takes the (as in computer fraud) or because the offer some competitive advantage to a competitor (as in industrial espionage). Data security also may have legal implications under the terms of the Data Protection Act — though that is the subject of another article. Data integrity implies the ensuring of remaining accurate, up-todate and valid — loss of integrity occurs because are either modified in some unauthorised way or are not modified and updated when the situation they represent changes (so that, for example, a stock control fails to record issues or receipts of stock and authorised users obtain an inaccurate stock report). For the purposes of this article, I shall use the term security to cover both of these aspects. The two terms can also be used with the prefix system rather than data to indicate loss of, or unavailability of, the entire — either because of a technical fault or accident. Most organisations take trouble to ensure that a breakdown causes minimum disruption to their IT processing — generally through having effective maintenance and repair procedures but this may also extend to having backup systems or failsafe processing agreements with other agencies. For particularly sensitive applications, faulttolerant systems (which normally have two processors and which mirror all files to a second disk) are available to ensure continuity of service. Such procedures are commonly used on mainframe and minicomputers but are often too expensive to implement on micros. However, the increasing use of networks based around a powerful server which contains large amounts of software and means that such techniques must be extended to this of operation. One common source (too common, unfortunately) of unavailability is program error. All programmes, both in-house and commercially supplied, contain some bugs — some are severe enough to bring the to a grinding halt. Only proper design and testing can eliminate this source of problems. It is to be hoped that software suppliers refrain from releasing early versions of software onto the market and expecting users to carry out the final testing. However, in the meantime it is important that users are educated to be aware of such problems and to use a routine which minimises loss in such cases, e.g. by saving word processing files at regular intervals. Similarly it is program and design that avoids many of the problems of unauthorised amendment of data. Many programs which involve valuable have authorisation processes which limit access of individuals to parts of the program or parts of the data. Thus it may be possible to assign read rights which enable a particular user to access on screen but not to make any changes. Other higher level users may be assigned read/write status allowing them to make amendments to the data. This status is normally provided by issuing specific identity codes and/or passwords to different classes of user. The protection is thus in two parts — the administrator assigns rights to different users and the software validates those rights by requesting the identification code or password before certain activities are allowed. Software controls also include the use of audit trails where the maintains some form of log of which users did what, and when. This may not directly prevent unauthorised access but it may be a means of tracking down culprits and in acting as a deterrent in the face of possible detection. Another software-related problem is that of conflicting programs. This occurs where a user has his or her favourite TSR (terminate and stay ready) program loaded into memory and then attempts to use another package which makes a bid for the same area of memory. Usually this simply results in the clash preventing the loading of the second package but it can result in memory corruption. If that part of memory is then saved to disk, it may overwrite a previous version of the datafile which was uncorrupted and the genuine, valid are lost. When attempting to use (especially more than one) TSR programs, the user should test their compatibility with sample that can be lost without worry. There are numerous stories about grand theft of money, or valuable data, from computing systems. When one tries to trace the source of such stories, it is often difficult to get back to a reliable source. This may be because the story is apocryphal based on rumour; or because the organisation that suffered the loss does not want publicity to be

The development of a hypertext‐based tutor for Geographical Information Systems

AbstractExperience gained in the construction of the world's first Geographical Information Systems tutor, ARCDEMO, emphasised the importance of accommodating different learning strategies. ARCDEMO, while highly successful, suffered from static graphical displays, a single pre‐determined access path, and an overall design which restricted its scope in use. The Geographical Information System Tutor (GIST) was developed to address these problems using Apple's object‐orientated HyperCard software. GIST incorporates a ‘point‐and‐click’ interface with graphical cues to initiate operations which include animated demonstrations, step‐by‐step illustrative graphics and graphical displays capable of user modification. The system was designed with two alternative access modes, serial or browsing, to allow different classes of user to work through the material in their preferred fashion. The use of GIST in undergraduate and short course teaching has shown how users respond well to the interface and find graphical explanations easy to follow.

Level of abstraction structured text

Computer users' negative reactions to printed computer documentation are attributed to the linear nature of the print medium, coupled with the varied information needs of different classes of users. A document system, called LAST (level of abstraction structured text), that meets the requirements of nonlinear traversal and automatic adjustment to users' requirements for type of information and level of detail is described. This system is a series of internally consistent text frames, organized by level of abstraction. It is shown that LAST system users made significantly fewer errors on task performance measures such as number of typing mistakes, correctly set margins and tabs, and correctly formatted text body. LAST users' subjective acceptance ratings of the documentation system were found to be higher than those given to the printed documentation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Controllability of computer performance tradeoffs obtained using controlled-share queue schedulers

Adjustable feedback schedulers control the relative performance obtained from a computer system by different classes of users. This work examines the control of relative throughputs (or related measures) by feedback of departure counts. Counts from key resources in the system are used to dynamically adjust the priorities of the different classes at certain queues in an attempt to achieve preset values of the ratios of the class throughputs. An iterative mean-value algorithm is given which approximates the throughputs actually achieved by this scheduler within a few percent of error. Limits of controllability are observed beyond which the achieved throughput ratios cannot follow the preset values. A characterization is given for this `controllable performance set'. It is also shown how, using this set, the scheduler can be tuned to have approximately optimal set points for the ratios.

A model for allocating car parking spaces in universities

In this paper a linear programming model has been presented for determining the optimum allocation of existing car parking facilities for different classes of users within a closed community, of which a university is a typical example.

A methodology for evaluating interactive system usage

A study of transaction logs from NLM's ELHILL system provided data on system feature usage and user search behavior. Several hypotheses were tested regarding the use of a pattern analysis methodology to represent and evaluate user behavior. Different classes of users (frequent, moderate, infrequent) were compared. The methodology is such that findings across different user groups (and different systems) can be compared.

Access Charges and Related Issues for Civil GPS Users

The Global Positioning System (GPS) will be a giant navigation utility paid for by the U.S. taxpayers. Access charges will permit the operational costs to be borne by those who actually use the system, both foreign and domestic, rather than by the taxpayers. Civil users who pay for a service will not be ignored, as they are now with the Transit system. User charges will permit operational continuity when the DoD no longer needs GPS. An implementation technique based on annual replacement of an LSI chip which decrypts the satellite message is described. A low annual charge is recommended to permit maximum system use and to optimize annual revenues. Counterfeiting is shown to be impractical, except by pirate radio transmissions. The design challenges related to interaction with military requirements, equitable costs for different classes of users, and the transition from one access chip to the next are described. Institutional issues are outlined, including who should develop the user charge technique. It is proposed that higher charges apply to those who purchase foreign-built equipment to promote U.S. employment, balance of payments, and to provide a return on the U.S. taxpayer investment in the system development. Those civil users who need maxium accuracy are frustrated with the Government policy of accuracy denial. This is described, and the probable development of differential GPS techniques to recover accuracy is evaluated. The creation of differential GPS standards is encouraged. Finally, another plea for greater civil user involvement in federal navigation planning is aired.