bluuebunny/crossref_metadata_2025 huggingface dataset:
Distributed computing in a NUMP (Non-Uniform Message-Passing) environment
Authors: Yang Cui-Qing
Published: October 2004

In this paper we propose a general framework of distributed computing in a NUMP environment. A NUMP (Non-Uniform Message-Passing) distributed environment is a computing environment in which both tightly-coupled, shared-memory systems and loosely-coupled, distributed computers are co-existent, and the time for message-passing is non-uniform between various systems. An environment with such hybrid components has become a common phenomenon in most academic and industrial communities. The issue of how to develop and execute programs that take advantage of all the resources available in a hybrid environment is an open issue in the research that carries both theoretic and pragmatic significance. The main topics involved include the development of new computational models for NUMP environment, operating system and language support for NUMP computing, methodologies in NUMP programming, principles of algorithm design for NUMP system, and so on. We deem that the research in NUMP computing will contribute in providing a unified framework for parallel and distributed computing, and in accomplishing better utilization of computing resources at large scale.
A portable and reusable RDBMS interface for Ada
Authors: Voketaitis Arnold M.
Published: October 2004

Most software systems must support the maintenance of structured data using non-volatile storage media, and therefore require an interface to a relational database management system (RDBMS). This interface should ideally enable the movement of data into and out from a generic form of storage media by servicing requests which assume nothing relative to the underlying data management facility or data store. This paper will address the issues regarding the type of interface which best satisfies this need and will describe a proposed solution along with its applications.
Concurrent object-oriented programming in
Classic-Ada
Authors: Nelson Michael L. , Mota Gilberto F. , Theologitis Vassilios
Published: October 2004

Although Ada supports concurrency and can thus be used as a concurrent programming language, it is not generally considered to be an object-oriented programming language. Classic-Ada is a preprocessor which adds the concepts of classes, inheritance, and dynamic binding to the Ada language. Classic-Ada is not billed as a concurrent object-oriented programming language, but it is possible to do anything in Classic-Ada that can be done in Ada. Thus, Classic-Ada can also serve as a concurrent object-oriented programming language. In this paper, we review the use of Classic-Ada in both concurrent and distributed environments.
A multimedia system based on MPEG video coding algorithm
Authors: Miyamoto Yoshihiro , Ohta Mutsumi , Yano Mitsuharu , Nishitani Takao
Published: October 2004

A multimedia player system has been developed. The player is a playback system of video, audio, and graphics recoded on a CD-ROM or received through an ISDN primary rate service. Both CD-ROM and ISDN primary rate services can carry about 1.5Mbit/sec information, but this rate is too low compared with original video data rate. Therefore, video data compression techniques are needed for realizing such systems. Coding algorithm of video and associated audio has been discussed by MPEG (Motion Picture Experts Group) in ISO-IEC/JTC1. In our system, video decoding algorithm is based on the MPEG standardized method [1]. Only CD-ROM interface is provided because of limited availability of ISDN applications at present.
Proposal of selection method test pictures in HDTV subjective quality assessments
Authors: Tachi Takeshi , Iai Satoru , Kitawaki Nobuhiko
Published: October 2004

This paper describes definitive and systematic rules for selecting HDTV still test pictures to be used for properly assessing high-quality factors.We extracted three elementary psychological factors: "vividness," "comfortableness" and "sharpness," dominating the impression of HDTV still pictures, by using `Semantic Differential Method.' And HVC-signal characteristics, in Munsell color space, correlating closely with these factors were defined as selection guidelines of pictures symbolizing high-quality TV.
Usage parameter control and bandwidth allocation methods for ATM-based B-ISDN
Authors: Yamanaka Naoaki , Sato Youichi , Sato Ken-ichi
Published: October 2004

This paper proposes a ATM traffic management scheme that utilizes a deterministic source traffic descriptor, a deterministic Usage Parameter Control (UPC) algorithm and a conservative statistical bandwidth allocation method. The scheme not only guarantees the QOS of all connections but also allows for large statistical multiplexing gain. The proposed method, therefore, creates an effective B-ISDN that offers cost-effective broadband variable bit-rate services.
A nonce-based protocol for multiple authentications
Authors: Kehne A. , Schönwälder J. , Langendörfer H.
Published: October 2004

The Kerberos authentication service, a part of MIT's Project Athena, is based on the Needham and Schroeder protocol. Timestamps depending on reliable synchronized clocks are used to guarantee the freshness of messages. As an improvement, we present a nonce-based protocol offering the same features as Kerberos. We generate a ticket in an initial message exchange which includes a generalized timestamp. Checking this generalized timestamp is left to the principal who created it. Consequently we do not need synchronized clocks. Our protocol has the property of using a minimal number of messages to establish an authenticated session key.
Architecture design for regulating and scheduling user's traffic in ATM networks
Authors: Chao H. Jonathan
Published: October 2004

The asynchronous transfer mode (ATM) technique provides a standardized and flexible scheme to transport and switch traffic effectively for different services. To provide satisfactory quality of service (QOS) to all users on the network, it is necessary to control the user's traffic so that network resources can be efficiently and fairly utilized by all the users while still meeting the individual QOS requirement. In this paper, we propose to control the user's traffic at two places in the network: at the user-network interface (UNI) by a traffic shaper or a traffic enforcer, and at the network-node interface (NNI) by a traffic regulator and a traffic scheduler. The traffic shaper/enforcer adopted in our work contains a buffer to delay and shape the violating cells that do not comply with some agreed-upon traffic parameters. The traffic regulator regulates cells at each network node to avoid long bursts being formed which may increase the network congestion probability. A traffic scheduler that follows the traffic regulator schedules the cells' departure sequences based on their delay priorites. We have proposed a general, feasible architecture to implement the traffic shaper, regulator, and scheduler, at various places in the network. A key component, the Sequencer chip, which contains 150k CMOS transistors, has been implemented to realize the architecture.
Analysis of a rate-based control strategy with delayed feedback
Authors: Fendick Kerry W. , Rodrigues Manoel A. , Weiss Alan
Published: October 2004

In this paper we analyze a class of delayed feedback schemes that achieves the dual goal of keeping buffers small and utilizations high, despite propagation delays and regardless of network rates. We analyze delayed feedback schemes as a system of delay-differential equations, in which we model the queue-length process and the rate at which a source transmits data as fluids. We assume that a stream of acknowledgements carries information about the state of a bottleneck queue back to the source, which adapts its transmission rate according to any monotone function of that state. We show stability for this class of schemes, in that their rate of transmission and queue length rapidly converge to a small neighborhood of the designed operating point. We identify the appropriate scaling of the model's parameters for the system to perform optimally.
An effective scheme for pre-emptive priorities in dual bus Metropolitan Area Networks
Authors: Liebeherr Jörg , Akyildiz Ian F. , Tantawi Asser N.
Published: October 2004

The IEEE 802.6 standard for Metropolitan Area Networks does not provide multiple priority traffic for connectionless data services. A priority mechanism that was considered for the standard showed to be not effective. As of now, there exists no protocol for multiple access dual bus networks that is able to implement pre-emptive priorites and, at the same time, can satisfy minimal fairness requirements for transmissions at the highest priority level. In this study, a protocol with strictly pre-emptive priorities, i.e., a protocol that does not admit low priority traffic if the load from high priority traffic exceeds the capacity of the transmission channel, is presented. The protocol is derived from a unique bandwidth allocation scheme with a full utilization of the bus capacity, with a fair distribution of bandwidth respective to traffic from a particular priority level and with pre-emptive priorities. The performance of the presented protocol is compared to a priority mechanism that is based on the bandwidth balancing mechanism. It is shown that adopting the new protocol results in shorter access delays for high priority transmissions.
Reliability and scaling issues in multicast communication
Authors: Rajagopalan Bala
Published: October 2004

The efficiency with which multicast communication can take place is largely determined by the network level support available for such communication. Two factors contribute to the complexity of supporting current multicast applications: the lack of reliable multicast transport mechanisms at the network level and the lack of network support for large scale multicast communication. In this paper, we examine the issues pertinent to eliminating these shortcomings. We first show that internet multicasting algorithms based on reverse path forwarding are inherently unreliable and present a source-tree-based reliable multicasting scheme. The new scheme makes use of simple inter-gateway protocols and works on top of previously developed distance vector and link state internet routing schemes. Next, to support large scale applications, we present a scheme for partial multicasting and introduce a new network level operation, called
gather
. The partial multicasting mechanism allows messages to be delivered to subsets of multicast destinations, while the
gather
operation aids gateways in selectively suppressing redundant messages, thus reducing the message complexity. Using simulations, we investigate the efficacy of our schemes in supporting a sample application based on multicast communication.
Pre-allocation media access control protocols for multiple access WDM photonic networks
Authors: Sivalingam Krishna M. , Bogineni Kalyani , Dowd Patrick W.
Published: October 2004

Media access control protocols for an optically interconnected star-coupled system with pre-allocated WDMA channels are introduced and compared. The photonic network is based on a passive star-coupled WDM–based configuration with high topological connectivity and low complexity. The channels are pre-allocated to the nodes with this approach, where each node has a
home channel
that it uses either for all data packet transmissions or all data packet receptions. A home channel may be shared if the number of nodes exceeds the number of channels in the system. This approach does not require both tunable transmitters and tunable receivers. The performance of a generalized random access protocol is compared to a protocol based on interleaved time multiplexing. Both protocols are designed to operate in a multiple-channel multiple-access environment and require each node to possess a tunable transmitter and a fixed (or slow tunable) receiver. Semi-markov analytic models are developed to investigate the performance of the two protocols. The analytic models are validated through simulation and performance is evaluated in terms of network throughput and packet delay with variations in system parameters.
Performance evaluation of Forward Error Correction in ATM networks
Authors: Biersack Ernst W.
Published: October 2004

If the packet loss rate in a network is higher than the loss rate requested by an application, the transport protocol must make up for the difference in loss rate. In high bandwidth delay-product networks the latency introduced by retransmission-based error recovery schemes may be too high for applications with latency constraints. In this case,
Forward Error Correction
(FEC) can be used. FEC allows recovery from loss without retransmission. The amount of loss recovered strongly depends on the loss behavior of the network. FEC works best if losses are dispersed in time.

We use simulation to study the loss behavior of an output buffered multiplexer for three different traffic scenarios. Our results show how the loss behavior of the multiplexer is affected by the traffic mix and the statistics of the sources. The more bursty the sources, the higher the loss rate and the higher the probability that losses will occur in bursts. Based on simulation results, we develop a mathematical model for the performance of FEC and compute the effectiveness of FEC for the three traffic scenarios. FEC is not effective for the two homogeneous traffic scenarios. However, FEC reduces the loss rate for the video sources by several orders of magnitude for a heterogeneous traffic scenario consisting of video and burst sources.
Efficient demultiplexing of incoming TCP packets
Authors: McKenney Paul E. , Dove Ken F.
Published: October 2004

When a transport protocol segment arrives at a receiving system, the receiving system must determine which application is to receive the protocol segment. This decision is typically made by looking up a protocol control block (PCB) for the segment, based on information in the segment's header. PCB lookup (a form of demultiplexing) is typically one of the more expensive operations in handling inbound protocol segment [Fe190].

Many recent protocol optimizations for the Transmission Control Protocol (TCP) [Jac88] assume that a large component of TCP traffic is bulk-data transfers, which result in packet trains [JR86]. If packet trains are prevalent, there is a high likelihood that the next TCP segment is en route to the same application (i.e. uses the same PCB) as the previous TCP segment. In these environments a very simple one-PCB cache like those used in BSD systems yields very high cache hit rates.

However, there are classes of applications that do not form packet trains, and these applications do not perform well with a one-PCB cache. Examples of such applications are quite common in the area of heads-down data entry into on-line transaction-processing (OLTP) systems. OLTP systems make heavy use of computer communications networks and have large aggregate-packet-rates but are also characterized by large numbers of connections, low per-connection packet rates, and rather small packets. This combination of characteristics results in a very low incidence of packet trains.

This paper uses a simple analytic approach to examine how different PCB lookup schemes perform with OLTP traffic. One scheme is shown to work an order of magnitude better for OLTP traffic than the one-PCB cache approach while still maintaining good performance for packet-train traffic.
Visualizing packet traces
Authors: Zinky John A. , White Fredric M.
Published: October 2004

This paper describes an environment for visualizing packet traces that greatly simplifies troubleshooting protocol implementations. Network management centers routinely collect packet traces to tally traffic statistics and to troubleshoot protocol configuration and implementation problems. Previous efforts have focused on the reliable collection of traces and their statistical interpretation. Display of packet traces was restricted to a textual representation of the raw headers. Our prototype environment interprets the trace as a whole. It identifies conversations across protocol layers, simulates the services offered by lower layers, and hides the lower layer implementation detail from the representation of higher layer conversations. Our prototype offers over a dozen different types of diagrams for showing protocol interactions and uses linked highlighting to show the relationships between the objects in different diagrams.
Creating structure from linearity in non-Ada interfaces
Authors: Campbell John A.
Published: October 2004

In many practical situations the ability to utilize Ada's capacity for data abstraction is compromised by the requirement to interface with memory resident data provided by previously designed software or hardware. A technique is presented for maintaining data abstraction by overlaying Ada structure on linear, unstructured data in a shared memory region.
The Task Dependence Net in Ada software development
Authors: Cheng Jingde
Published: October 2004

Recently, the author proposed two new types of basic program dependences in concurrent programs, named the synchronization dependence and the communication dependence, and a new program representation for concurrent Ada programs, named the Task Dependence Net (TDN), which extends the usual program dependence graph for sequential programs to the case of concurrent Ada programs. This article discusses some potential applications of the task dependence net in Ada software development activities including program understanding, testing, debugging, maintenance, and complexity measure/metrics.
Entity-relationship modeling
Authors: Campbell David
Published: October 2004

In the business environment data modeling diagrams are used as a user communication tool during Data Analysis, as a Database Design tool, as part of Systems Documentation and, increasingly, as a base for automatic generation of data definition language statements by CASE software.In this paper it is argued that the first two uses have conflicting requirements and that there is a need for a separate, more appropriate, nomenclature and notation for user communication than that which is currently in use.A modified form of Chen's approach is considered and rejected in favour of a Resource-Activity diagram.The conversion of this to an Entity diagram, and thence to Relational form is briefly discussed.Implications for the design of CASE tools and the adoption of a CASE standard are considered.
Videotex systems
Authors: Ghosh Deb
Published: October 2004

Videotex
refers to "various computer-based interactive systems that electronically deliver screen text, numbers and graphics via telephone or two-way cable for display on a television set or a video monitor". This technology allows computer-naive users to easily access general interest or highly specialized information stored in on-line databases in the amount and sequence (s)he desires. Over the past decade, there has been considerable interest in videotex systems, and a number of them have already been implemented in different countries. With the proposed implementation of Integrated Services Digital Networks, the interest in videotex systems is expected to grow even further.This paper provides a brief overview of commercial videotex systems in various countries, and discusses possible organizational usage of these systems. In addition, this paper discusses design issues considered central to the development of a geographically dispersed videotex systems. Currently available solution procedures for addressing these design issues are also suggested.
Information resource management
Authors: March Salvatore T. , Kim Young-Gul
Published: October 2004

Information-based organizations depend upon computer databases and information systems for their ongoing operation and management.
Information Resource Management (IRM)
is a program of activities directed at making effective use of information technology within an organization. These activities range from global corporate information planning to application system development, operation, and maintenance and support of end-user computing. Numerous approaches to specific IRM activities have been proposed. They remain disjoint, however, and, hence globally ineffective.A significant reason for inability to integrate IRM activities is the failure to adequately define the information resource. What is it that must be effectively managed? This paper addresses this issue. It applies data modeling concepts to the problem of managing organizational information resources. A data model is developed to support and integrate the various IRM activities. This model formally defines the information resource and the data needed to manage it. It provides a basic ingredient for effective Information Resource Management.
An assessment of institutional research productivity in MIS
Authors: Grover Varun , Segars Albert H. , Simon Steven J.
Published: October 2004

In this study, major MIS research institutions are identified and ranked based on their contributions to quality MIS publication outlets. Over 10,000 pages of research generated over the past decade (1982-1991) are credited to voer 190 institutions. The top 50 institutions are ranked. The method followed is similar to other studies conducted in well-established research areas in business, such as finance, marketing and economics. The results provide objective and useful information to the profession.
Research issues in hypertext and hypermedia for business applications
Authors: Mahapatra Radha K. , Courtney James F.
Published: October 2004

Hypertext and hypermedia provide a mechanism to store and retrieve unstructured, related information in a meaningful way. This new technology has the potential to extend the use of computers into areas, until recently considered to be outside the realm of computerization. This article identifies a number of application areas in the business domain that can benefit from the use of hypertext. It also identifies a number of research issues that must be addressed before business organizations can reap the benefit of this novel technology.
Automated interface code generation from Ada specifications
Authors: Pukite Paul R.
Published: October 2004

Mapping data structures between incompatible representations remains an error-prone and tedious part of program development. This letter outlines a method for automating interface code generation based on Ada package specifications and the use of Ada keywords as interface mapping directives. This concept supports information hiding by placing the details of the generated interface code in the package body.
Experiences with the partitions model
Authors: Dobbing Brian
Published: October 2004

Alsys has implemented a distributed Ada system known as
AdaMap
which is based on a program partitioning model almost identical to that being proposed for Ada9X, although the user interface for the inter-partition communications system is based on an input-output package rather than on remote procedure call. This paper examines the benefits of the partitions model including a simple demonstration program built using AdaMap, and is intended to give confidene in the viability of the partitions model for Ada9X.
Translating an AdaPT partition to Ada9X
Authors: Goldsack S. J. , Holzbacher-Valero A. A. , Volz R. , Waldrop R.
Published: October 2004

This paper shows how the concept of
Partitions
introduced in the work of an earlier workshop [Gargaro 90a] as a possible feature to support the development of secure distributed systems in Ada9x is closely related to the abstract data type packages in the new form of Ada and can benefit from the inheritance features of the new language.It is considered that the close relationship of objects supported in the object-oriented features of the new Ada and the partitions introduced in the earlier work should be exploited in the Ada9x distribution model.
Computational geometry column 18
Authors: O'Rourke Joseph
Published: October 2004

Results on visibility graphs are classified and organized into five tables.
Applications of graph drawing to software engineering (abstract)
Authors: Batini Carlo
Published: October 2004

Several conventions for drawing rooted trees are discussed: classical drawings, tip-over drawings, inclusion drawings, and h-v drawings. In each convention, a number of algorithms and complexity results are available. For free trees (no specific root), algorithms are mostly drawn from folklore. Radial drawings, spring drawings, and orthogonal drawings are discussed.
Algorithms for drawing trees (abstract)
Authors: Eades Peter
Published: October 2004

In several application areas of software engineering intermediate and final products of the design activity are represented by means of diagrams. Diagrams present several advantages over other representations, since they are an aid to clear thinking (a diagram is better that a thousand words). Diagrams are external representations of organization charts, data and function schemas, structure of procedure calls, pieces of code, etc. A diagram is characterized by a meaning (the "piece of reality" it draws), and a syntax, expressed by: a graphic grammar, that defines the types of symbols and connections allowed, aesthetic criteria adopted in drawing the diagram. an underlying diagram model (e.g. hierarchical, planar, connected, etc). In software engineering tools, diagram are manipulated by several functions, such as beautification, modification, refinement, merging of several diagrams, animation, etc. Each one of such functions is characterized by specific algorithms needed for the final activity of diagram drawing. E.g. when we beautify a diagram we are interested to achieve some aesthetic criteria that were previously not respected; when we refine a diagram into a more detailed one, we are interested to maintain monotonicity of shape. Producing incrementally such a library by dynamically tailoring and merging paradigmatic algorithms, results in a new and interesting research area.
Partial orders for planarity and drawings (abstract)
Authors: de Fraysseix Hubert , Rosenstiehl Pierre
Published: October 2004

A bipolar orientation of a graph appears often in the algorithm literature as a first step for the generation of a particular drawing. Here the properties of bipolar orientations are systematically explored in terms of circuits, cocircuits, rank activities, Tutte polynomial, poset dimension, angle bipartition and max flow-min cut theorem. Efficient algorithms are described to list, generate or extend bipolar orientations for general graphs or plane ones, with or without constraints. (Joint work with Patrice de Mendez.)
Area requirements (abstract)
Authors: Di Battista Giuseppe
Published: October 2004

A compound diagraph is a directed graph with both inclusion and adjacency edges and is widely used in diverse fields. In this talk, first, a heuristic method for automatically drawing a compound digraph is presented. Then, several graphic interface techniques which facilitate the method in organizing ideas such as direct manipulation, animation, incremental editing, fish-eyes (focusing, abridgements), and utilization of curves are discussed. Finally, it is emphasized that interface issues are important as well as algorithmic aspects of graph drawing. (Joint work with K. Misue.)
Angular resolution of straight-line drawings (abstract)
Authors: Kaufmann Michael
Published: October 2004

An orthogonal drawing of a graph is such that the edges are represented by polygonal chains consisting of horizontal and vertical segments. The intermediate vertices of the chain (which are not vertices of the graph) are called bends. In this talk we survey algorithms for constructing planar orthogonal drawings. The main quality measures considered are the minimization of the number of bends and of the area of the drawing. The construction of planar orthogonal drawings has many important applications, including graph visualization, VLSI layout, facilities floorplanning, and communication by light or microwave. Given an embedded planar graph
G
with
n
vertices, a planar orthogonal drawing of
G
with the minimum number of bends can be computed in
O
(
n
2
log
n
) time using network-flow techniques. Drawings with
O
(n)
bends can be constructed in
O
(n)
time using visibility representations. Also, there are families of graphs that require Ω
(n)
bends. Open problems include minimizing bends over all possible embeddings, and finding an efficient parallel algorithm for bend minimization.
Circle packing representation in the plane and other surfaces
Authors: Mohar Bojan
Published: October 2004

The angular resolution of a drawing of graph
G
is the minimum angle between two incident edges that appears in the drawing. In this talk the state of the art is presented how to maximize the angular resolution. First the general technique by Formann et al. [FOCS'90] is reviewed, then a refinement for planar graphs is given. A recent paper of Malitz/Papakostas [STOC'92] shows that planar graphs can be drawn planar with minimum angle only depending on the maximum degree of the vertices. At the end, some aspect on the relationship of resolution and area are discussed.
Dynamic graph drawing (abstract)
Authors: Cohen Robert F.
Published: October 2004

An automatic layout facility is a tool that receives as input a graph-like structure and is able to produce a diagram that nicely represents such a structure. Because of the increasing number of systems that manage diagrams, automatic layout facilities and algorithms for graphs layout have been extensively studied in the last years. We present a new approach in designing an automatic layout facility. Our approach is based on a modular management of a collection of algorithms and on a tool that is able to automatically select the best algorithm for a given application. Such approach has been used for devising the automatic layout facility of Diagram Server, a network server that offers to its clients several facilities for managing diagrams. (Joint work with P. Bertolazzi and G. Di Battista.)
A new method for planar graph drawings on a grid (abstract)
Authors: Kant Goos
Published: October 2004

Drawing graphs is an important problem that combines flavors of computational geometry and graph theory. Applications can be found in a variety of areas including circuit layout, network management, software engineering, and graphics. The main contributions of this paper can be summarized as follows:
(i)
We devise a model for dynamic graph algorithms, based on performing queries and updates on an implicit representation of the drawing, and we show its applications.
(ii)
We present several efficient dynamic drawing algorithms for trees, series-parallel digraphs, planar
st
-digraphs, and planar graphs. These algorithms adopt a variety of representations (e.g., straight-line, polyline, visibility), and update the drawing in a smooth way.
(iii)
We show that the implicit representation of the layout used by our algorithms for trees and series-parallel digraphs also supports point-location and window queries. (Joint work with P. Bertolazzi, G. Di Battista, R. Tamassia, and I. G. Tollis.)
Vague text compression
Authors: Davison Andrew
Published: October 2004

A new approach to the "lossy" compression of text is described, based on the computational benefits of reading handwritten text, as opposed to text set in a more formal typographical style. Specifically, a new class of fonts, called
vague fonts
, are proposed which encode the vagueness of handwriting. Text written using a vague font can be compressed to a much greater degree than the same text represented in a conventional font.
Telecommunications technologies
Authors: Grover Varun , Goslar Martin
Published: October 2004

Technologies associated with telecommunications and computing are rapidly converging. It is therefore becoming difficult for IS practitioners to ignore telecommunications technologies and important for IS researchers to begin investigating them. This paper identifies a set of representative telecommunications technologies, and reports the results of a study undertaken to assess their usage in American industry. The data identifies technologies that are prominent and innovative as perceived by the executives surveyed.
Distribution in a single address space operating system
Authors: Chase Jeff , Issarnay Valérie , Levy Hank
Published: October 2004

The recent appearance of architectures with flat 64-bit virtual addressing opens an opportunity to reconsider the way our operating systems use virtual address spaces. We are building an operating system called Opal for these wide-address architectures. The key feature of Opal is a single global virtual address space that extends to data on long-term storage and across the network. Hardware-enforced memory protection exists within this single address space.This paper outlines our ideas for extending Opal to a distributed environment, focusing on the naming and binding of data and services to allow uniform treatment across the network. Our central point is that although the
meaning
of names (i.e., the entities denoted by those names) should be uniform throughout the network, at a lower level the
binding
of names to physical data or servers may vary with the node uttering the name, in order to accommodate caching, replication, and migration. This principle affects Opal's handling of both data names (virtual addresses) and resource names (capabilities).
The use of name spaces in Plan 9
Authors: Pike Rob , Presotto Dave , Thompson Ken , Trickey Howard , Winterbottom Phil
Published: October 2004

Plan 9 is a distributed system built at the Computing Sciences Research Center of AT&T Bell Laboratories over the last few years. Its goal is to provide a production-quality system for software development and general computation using heterogeneous hardware and minimal software. A Plan 9 system comprises CPU and file servers in a central location connected together by fast networks. Slower networks fan out to workstation-class machines that serve as user terminals. Plan 9 argues that given a few carefully implemented abstractions it is possible to produce a small operating system that provides support for the largest systems on a variety of architectures and networks. The foundations of the system are built on two ideas: a per-process name space and a simple message-oriented file system protocol.
On the role of compression in distributed systems
Authors: Douglis Fred
Published: October 2004

Compression has been used in numerous ways for many years, but recently two factors have combined in a way to push compression to the forefront of distributed systems. First, the disparity between processor speeds and I/O rates is ever-increasing, making it possible to perform compression in software to a much greater extent than was previously feasible. Second, the growth of new applications demanding enormous data rates, such as digital video and audio, makes hardware compression increasingly desirable: I discuss the importance of compression in various environments and describe how compression may be used not only to reduce the demand for disk space, disk bandwidth, and network bandwidth, but also to appear to extend physical memory.
Transparency and reflection in distributed systems
Authors: Stroud Robert
Published: October 2004

The recursive composition of systems to form functionally equivalent transparently distributed systems is an important paradigm for constructing distributed systems. The extent to which such recursive transparency can be achieved depends crucially on the semantics and functionality offered by the underlying systems. It is therefore important that systems should be designed so that their functionality scales gracefully in a distributed environment.In order to build a transparent extension to a system, it is necessary to be able to intercept its basic operations and extend their meaning to a distributed environment. This requires the underlying system to have a clean structure with well-defined interfaces and the reflective capability necessary to intercept and extend operations crossing those interfaces. Thus, both reflection and transparency are important aspects of the design of extensible distributed systems.It is possible to make transparent extensions to object-oriented systems built on top of micro-kernel architectures but the lack of reflective capabilities in the current generation of object-oriented programming languages can make this unnecessarily awkward. More research is required to develop languages whose computational model and implementation are a better match for the underlying platforms which support them.
Static and dynamic polling mechanisms for fieldbus networks
Authors: Raja Prasad , Noubir Guevara
Published: October 2004

Real-time local area networks like Fieldbus have to handle two types ofdata transfer, synchronous and asynchronous. The synchronous data is generated periodically and has to be transmitted before fixed deadlines. Asynchronous messages are generated by unforeseen events and thus cannot be predicted. The data transfer is handled in two different phases or time---windows. In this paper, we apply different algorithms that are known from the real-time schedluing discipline for real-time communication networks. Simplifications are made with respect to frame lengths and the resulting error is shown to be negligible for the type of data transfer considered. The algorithms generate the correct polling sequence for the data transfer automatically respecting the periodic deadlines. We also introduce dynamic mechanisms to extend time-windows and utilize the network bandwidth more efficiently. These algorithms are computed during the real-time operation of the network.
GRPC
Authors: Wang Xingwei , Zhao Hong , Zhu Jiakeng
Published: October 2004

RPC (Remote Procedure Call) is very popular in distributed application design. However, most existing RPC systems have some defects on parallelism and reliability and transparency, they can only support point-to-point and(or) broadcast communication. We try to bring the process group concept into RPC systems and present a new kind of communication cooperation mechanism supporting the cooperation among distributed entities in distributed systems. We call it GRPC(Group Remote Procedure Call) mechanism. According to different application background, the related GRPC mechanism are named
lookup, function-convergence
and
update
GRPC. The prototype systems of these three specific classes of GRPC mechanisms have been implemented in the local area network which consists of SUN 4 workstations. The performance evaluation on these prototype systems has been made. Practice has shown: the GRPC mechanism can not only improve the parallelism, reliability and transparency of RPC systems, but also enable RPC systems to support group communication.
A multitasking executive for operating systems courses
Authors: Haro Christophe , Proust Christian
Published: October 2004

This paper presents the design of a multitasking executive for a course on computer operating systems. The system described here allows us to illustrate some fundamental concepts of multiprocessing and to experiment parallel programming.The system built is a preempt multitask one, which implements semaphore as a synchronisation tool of concurrent programs. A software layer called SESSION MANAGER is built above the basic kernel which is hence isolated from user's processes.The whole system is thus conceived to be written and tested by students during their courses on basic systems.
On the outer
Authors: Toynbee Claire
Published: October 2004

After more than three years researching the question "Why women drop computer science" at Victoria University of Wellington in New Zealand, I am surprised so many women succeed given the overwhelming odds against them. Women who take computer science are 'different' not simply because they are women, but because they have chosen a subject which has been primarily a male domain. Once enrolled, they find themselves 'on the outer', facing difficulties not usually experienced by white middle class men who take computer science. There is evidence that other minorities also suffer alienation in what is essentially a distinct subculture whose origins will be discussed later.
Specification versus implementation based on Estelle
Authors: Kovacs L , Ercsényi A
Published: October 2004

The main problems of the ESTELLE communication protocol specification language are discussed by analyzing the present version of the ISO draft proposal language definition. Two different directions of the future development of ESTELLE are proposed. The first is the creation of the exact, formal semantic definition. The second direction of the language development leads to the high-level implementation languages. The separability technique (separate compilation) which can be used in the case of ESTELLE documents is investigated and a different structuring principle is suggested. The inner contradiction of the module instantiation is revealed and the construction of an alternative specification is suggested. The ESTELLE process concept is compared with an implementation process concept. Analyzing the structures of the protocol specifications it is pointed out that some implementation considerations are smuggled into the protocol specifications described in ESTELLE.
Hints for the interpretation of the ISO session layer
Authors: Caneschi F
Published: October 2004

This work originated from discussions on the interpretation of the ISO 8327 Session Protocol and the ISO 8326 Session Service. The author, who participated in the development of the above mentioned documents, discovered that many who attempted a thorough reading of them, either for implementing the Session layer or for a better understanding of the protocol, had a number of questions regarding the interpretation of the documents.There are two principal reasons for these difficulties. First, the state table description of the protocol in Appendix A of ISO 8326 and ISO 8327 is not formal, and thus subject to different interpretations. Second, there are actions which are not explained in Appendix A, but rather are described in the text. This means that even after having solved all questions related to Appendix A, one cannot be sure that an implementation is in fact correct.This paper is intended as an aid in interpreting the documents, and to correlate the plain text description to the state table description.A number of persons contributed to the contents of this paper, and it is impossible to list them all. The author, however, wishes to mention the major discussions that had with Albert Fleischmann and Stefan Pappe during their implementation of the Heidelberg Session layer; Colin West of the Zuerich Lab when he was attempting to devise a testing strategy for the above mentioned implementation; and Marten van Sinderen of the Twente University and Giuseppe Scollo of the Catania University when using LOTOS to describe the ISO Session layer.Wolfgang Effelsberg and Jim Staton of E. N. C., finally, deserve special thanks for their many valuable suggestions, both technical and structural, that they gave on the early versions of this document, which could now be titled "Hints for the interpretation of "Hints for the interpretation of the ISO Session Layer"".
Moving from DoD to OSI protocols: A first step
Authors: Witt M
Published: October 2004

Recently, there has been a great deal of interest in the possibility that the U.S. Department of Defense might transition to the use of the OSI Protocol Standards. There are many difficult issues involved in such a transition. This paper takes a brief look at the general issues involved and then proposes a first step toward OSI compatibility - the ability for DoD and OSI protocols to coexist on the same network. This is achieved through the implementation of a "Dual-IP Gateway", which supports both the DoD and OSI Internet Protocols.
Development of computer-based information systems: A communication framework
Authors: Guinan Patricia , Bostrom Robert P
Published: October 2004

It is still too often the case that Computer-Based Information Systems (CIS) are developed behind schedule, overcost, do not do as much as promised, and do not satisfy their users. In the last few years, we have been bombarded by techniques, methods, "optimal ways" in which to approach system development. For example, techniques such as prototyping and data flow diagrams have been developed to make the requirements definition process more effective. These methods, provide direction and structure to the development process.
Wide-address spaces
Authors: Bartoli Alberto , Mullender Sape J. , van der Valk Martijn
Published: October 2004

In a recent issue of Operating System Review, Hayter and McAuley [1991] argue that future high-performance systems trade a traditional, bus-based organization for one where all components are linked together by network switches (the Desk-Area Network). In this issue of Operating System Review, Leslie, McAuley and Mullender conclude that DAN-based architectures allow the exploitation of shared memory on a wider scale than just a single (multi)processor. In this paper, we will explore how emerging 64-bit processors can be used to implement shared address spaces spanning multiple machines.
Fine grained object protection in UNIX
Authors: Low Marie Rose , Christianson Bruce
Published: October 2004

In this document we describe and discuss a solution, called UNIX Access Table Protection (UATP), to the problem of providing a secure environment for persistent object types with fine grained protection on a UNIX system. UATP requires no modifications to the UNIX kernel. User's on UNIX have discretionary access control over their directories and files. By using these controls in a particular way, this paper shows a way in which a hierarchy of protection domains can be set up to enable object methods and type instances to be managed securely and to be protected from unauthorised use. The document also describes how a particular object type, a UATP-kernel, which executes in these protection domains (in the same way as all other objects) can be used to provide fine grained protection for all other objects which are installed and running in the manner described here.
Implementation and evaluation of alternative process schedulers in MINIX
Authors: Guerrero R. , Leguizamon L. , Gallard R.
Published: October 2004

Minix is a Unix clone Operating System, designed by Tanembaum ([2],[3]) to allow beginners to do practical training in Operating Systems area.In this context the present paper describes the work done by a group of students implementing alternative process schedulers disciplines and their evaluation comparing performance estimates.Some unexpected deviations in the original implementation (Minix V. 1.0), found during software development, are also reported.
An Ada solution to the general mutual exclusion problem
Authors: Yue Kwok-bun
Published: October 2004

Although some specific mutual exclusion problems have been studied extensively, automatic solutions to synchronize general mutual exclusion problems with arbitrary mutual exclusion constraints have not been fully explored. This paper discusses an Ada 83 solution that can be applied to any general mutual exclusion problem. This solution is based on strong binary semaphores. A generic package is used to generate the solution for an given mutual exclusion problem. An Ada program for the simulation of the classical Dining Philosophers Problem is presented as an example to demostrate how the solution can be used.
Object oriented programming and virtual functions in conventional languages (an extended abstract)
Authors: Johansson Henrik
Published: October 2004

The Ada language can be used as an object oriented language with simulated multiple inheritance and late binding, if only some simple programming rules stated here are used. This enhances the possiblities of code reuse without violation of the strict type checking in the language. The dependencies between separate compilable libarary units can be reduced to a minimum, which is a major obstacle for writing reusable Ada code.