bluuebunny/crossref_metadata_2025 huggingface dataset:
Locality-aware request distribution in cluster-based network servers
Authors: Pai Vivek S. , Aron Mohit , Banga Gaurov , Svendsen Michael , Druschel Peter , Zwaenepoel Willy , Nahum Erich
Published: October 2004

We consider cluster-based network servers in which a front-end directs incoming requests to one of a number of back-ends. Specifically, we consider
content-based request distribution:
the front-end uses the content requested, in addition to information about the load on the back-end nodes, to choose which back-end will handle this request. Content-based request distribution can improve locality in the back-ends' main memory caches, increase secondary storage scalability by partitioning the server's database, and provide the ability to employ back-end nodes that are specialized for certain types of requests.As a specific policy for content-based request distribution, we introduce a simple, practical strategy for
locality-aware
request distribution (LARD). With LARD, the front-end distributes incoming requests in a manner that achieves high locality in the back-ends' main memory caches as well as load balancing. Locality is increased by dynamically subdividing the server's working set over the back-ends. Trace-based simulation results and measurements on a prototype implementation demonstrate substantial performance improvements over state-of-the-art approaches that use only load information to distribute requests. On workloads with working sets that do not fit in a single server node's main memory cache, the achieved throughput exceeds that of the state-of-the-art approach by a factor of two to four.With content-based distribution, incoming requests must be handed off to a back-end in a manner transparent to the client,
after
the front-end has inspected the content of the request. To this end, we introduce an efficient
TCP handoflprotocol
that can hand off an established TCP connection in a client-transparent manner.
Fast out-of-order processor simulation using memoization
Authors: Schnarr Eric , Larus James R.
Published: October 2004

Our new out-of-order processor simulatol; FastSim, uses two innovations to speed up simulation 8--15 times (vs. Wisconsin SimpleScalar) with no loss in simulation accuracy. First, FastSim uses speculative direct-execution to accelerate the functional emulation of speculatively executed program code. Second, it uses a variation on memoization---a well-known technique in programming language implementation---to cache microarchitecture states and the resulting simulator actions, and then "fast forwards" the simulation the next time a cached state is reached. Fast-forwarding accelerates simulation by an order of magnitude, while producing exactly the same, cycle-accurate result as conventional simulation.
Performance of database workloads on shared-memory systems with out-of-order processors
Authors: Ranganathan Parthasarathy , Gharachorloo Kourosh , Adve Sarita V. , Barroso Luiz André
Published: October 2004

Database applications such as online transaction processing (OLTP) and decision support systems (DSS) constitute the largest and fastest-growing segment of the market for multiprocessor servers. However, most current system designs have been optimized to perform well on scientific and engineering workloads. Given the radically different behavior of database workloads (especially OLTP), it is important to re-evaluate key system design decisions in the context of this important class of applications.This paper examines the behavior of database workloads on shared-memory multiprocessors with aggressive out-of-order processors, and considers simple optimizations that can provide further performance improvements. Our study is based on detailed simulations of the Oracle commercial database engine. The results show that the combination of out-of-order execution and multiple instruction issue is indeed effective in improving performance of database workloads, providing gains of 1.5 and 2.6 times over an in-order single-issue processor for OLTP and DSS, respectively. In addition, speculative techniques enable optimized implementations of memory consistency models that significantly improve the performance of stricter consistency models, bringing the performance to within 10--15% of the performance of more relaxed models.The second part of our study focuses on the more challenging OLTP workload. We show that an instruction stream buffer is effective in reducing the remaining instruction stalls in OLTP, providing a 17% reduction in execution time (approaching a perfect instruction cache to within 15%). Furthermore, our characterization shows that a large fraction of the data communication misses in OLTP exhibit migratory behavior; our preliminary results show that software prefetch and writeback/flush hints can be used for this data to further reduce execution time by 12%.
A study of protection in programming languages
Authors: Ambler Allen L. , Hoch Charles G.
Published: October 2004

The concept of “protection” in programming languages refers to the ability to express directly in the language the desired access control relationships for all objects defined in the language. The use of such mechanisms as
data types, scope, parameter passing
mechanisms,
routines as parameters, abstract data types,
and
capabilities
in Pascal, Concurrent Pascal, Euclid, Clu, and Gypsy are explored via a simple example which embodies many protection problems. The usefulness of language defined and enforced protection mechanisms to the process of formal verification is discussed.
Language features for process interaction
Authors: Andrews Gregory R. , McGraw James R.
Published: October 2004

Languages for parallel programming should meet four goals: expressiveness, data integrity, security, and verifiability. This paper presents a set of language features for describing processes and process interaction, gives examples of their use, and briefly discusses their relation to the goals. Two constructs, resources and protected variables, are introduced as the mechanisms for describing interaction. Resources are extensions of the monitor concept of Hoare; protected variables are global variables which can only be accessed by one process at a time. Two types of access control are introduced: restrictions on scope rules for static access, and capabilities for dynamic access. Examples include the interface to machine devices, files and virtual devices, readers/writers, device scheduling, device reservation, and buffer allocation.
Abstraction and verification in Alphard
Authors: Shaw Mary , Wulf Wm A. , London Ralph L.
Published: October 2004

The Alphard
form
provides the programmer with a great deal of control over the implementation of abstract data types. In this paper we extend the abstraction techniques from simple data representation and function definition to the
iteration statement
, the most important point of interaction between data and the control structure of the language itself. We introduce a means of specializing Alphard's loops to operate on abstract entities without explicit dependence on the representation of those entities. We develop specification and verification techniques that allow the properties of the
generators
for such iterations to be expressed in the form of proof rules. We obtain results for common special cases of these loops that are essentially identical to the corresponding constructs in other languages. We also provide a means of showing that a generator will terminate.
Portability and the UNIX operating system
Authors: Cañas Daniel A. , Esquivel Laura M.
Published: October 2004

This paper studies the compatibility degree between two different UNIX
2
environments. The porting of ConcurrenC (concurrent version of the C programming language) from a VAX
3
computer under UNIX 4.2BSD to an AT&T UNIX PC running UNIX System V was used as a testbed.ConcurrenC is analyzed to highlight the existence of the 4.2BSD features missing in UNIX System V. These characteristics are mainly related to system calls used for interrupt handling, and for process synchronization and communication. They are implemented under System V using new provided facilities (i.e., message mechanism for interprocess communication), or simulating their functioning through special purpose C language routines.
Developing a heterogeneous distributed operating system
Authors: Sun Zhongxiu , Xue Xing , Zhou Jianqiang , Yang Peigen , Xu Xihao
Published: October 2004

This paper describes the design and current status of a heterogeneous distributed operating system project called ZGL. This project is characterized by its attempt to provide for heterogeneity in both the use of hardware and the use of multiple existing operating systems. The existing operating systems are extended in a way that programs written for a single machine environment will be executed in the network environment without modification or recompilation but still can take advantage of shared hardware and software resources provided by other systems. In order to accommodate this heterogeneity, the project follows the client/server model, and uses a common communication interface for heterogeneous existing client systems to access shared services.
Composable Ada software components and the re-export paradigm
Authors: Bardin Bryce , Thompson Christopher
Published: October 2004

One of the goals of the software engineering community has been the establishment of a reusable software components industry. With increasingly wide acceptance of the Ada language, many of us feel that this goal may be within reach. The Ada language provides a powerful abstraction facility with constructs such as packages, user-defined types, and generic units with which to construct such components.However, the successful development of reusable software components written in Ada depends also upon the language's abstraction composition qualities. That is, it depends on how easily smaller abstractions (or components) may be combined to create larger and more powerful abstractions.This paper discusses in detail the most important methods by which abstractions may be composed in Ada and their limitations. A companion paper, titled "
Using the Re-Export Paradigm to Build Composable Ada Software Components
", will be published in a succeeding issue of Ada LETTERS. It demonstrates the techniques described here and concludes with suggestions for improvements that would enhance the composability of Ada software.
The algorithm capture approach to Ada transition
Authors: Wood D.
Published: October 2004

The mandate for the use of the Ada language in Department of Defense software systems, as well as the growing interest in Ada that exists in the commercial software industry, has created the need for planned, systematic transition paths from existing programs to Ada programs. The demands that Ada places on the life-cycle development of software increases the need for careful planning in any Ada transition effort. At the same time, the desire to derive Ada systems from an existing non-Ada baseline also increases the need for careful control of the transition process. This paper examines the general issues behind such a transition, and describes a transition process geared toward maximizing the benefit of the use of the Ada language, while maintaining a tightly-controlled link with existing systems.
Timing variation in dual loop benchmark
Authors: Altman N. , Weiderman N.
Published: October 2004

Benchmarks that measure time values using a standard system clock often employ a dual loop design. One of the important assumptions of this design is that textually identical loop statements will take the same amount of time to execute. This assumption has been tested on two bare computers with Ada® test programs and has been demonstrated to be inaccurate in these specific test cases.
OSI service specification with CCITT-SDL
Authors: Hogrefe Dieter
Published: October 2004

This paper shows how OSI architectural concept of service can be expressed using the specification language CCITT-SDL. Some general remarks about service specification using asynchronously communicating processes are followed by the introduction of a generalized form of the well-known time-sequence diagrams. This generalized form of time-sequence diagrams is is especially suitable for the semi-formal description of services rendered by asynchronously communicating service providers. Two examples, a Data Link and a Network service, show the application of the concepts developed here.
End-user computing by top executives
Authors: Hackathorn Richard D.
Published: October 2004

This paper examines the activities and perspectives of top executives towards end-user computing. End-user computing (EUC) is defined as "an information processing activity in which the person has direct personal control over all stage of the activity." Hence, the end user directly uses personal computers and related technology and does not necesarily have technical experience and training in the management information systems (MIS) area.The key issue is whether top executives from a unique group of users or whether they can be considered similar to other users in terms of support and control policies.A field study was conducted resulting in 239 respondents from a variety of organizations. Using the executive level of each respondent as the independent variable, eight other variables were examined such as: the extent of PC usage, exchange of data with others, use of programs developed by others, development of programs for use by others, access to corporate data remotely, etc.The data analysis show that, for the most part, executives do act and feel similar to others relative to end-user computing, which is a significant result. In other words, executives are active adopters of EUC technology and probably have a strong influence on EUC activities in their organizations. They frequently exchange PC data with others and develop programs or models for others. Therefore, considerations about executives as end users should be an important part of EUC policies, both for support and control.
Identifying early adopters of large software systems
Authors: Ball Leslie D. , Dambolena Ismael G. , Hennessey Hubert D.
Published: October 2004

In recent years the software industry has undergone rapid growth, yet little is known about the software acquisition process. This study examines the relationship between the acquisition of large data base management systems (DBMSs) and several characteristics of organizations and their personnel. Seven hypothesis related to the adoption of DBMSs are tested through a survey and the results are reported.
Image base management system: a promising tool in the large office system environment
Authors: Felician Leonardo
Published: October 2004

Data base systems are now faced with a new application field---Image Based Systems. An "image" is simply a digitalized document page stored as a bit string. Applications in office automation include filing, large multimedia data bases, library storage and retrieval, and in science and medicine the recording and storage of satellite, geological and body scanner pictures. This paper defines the requirements for an architecture of an image base management system (IBMS) stored on large magnetic and optical disks and points out the problems introduced by the nonerasable constraint of optical disks. Suitable data structures and the main algorithms to manage an image base are discussed in details.
A survey of process migration mechanisms
Authors: Smith Jonathan M.
Published: October 2004

We define process migration as the transfer of a sufficient amount of a process's state from one machine to another for the process to execute on the target machine.This paper surveys proposed and implemented mechanisms for process migration. We pay particular attention to the designer's goals, such as performance, load-balancing, and reliability. The effect of operating system design upon the ease of implementation is discussed in some detail; we conclude that message-passing systems simplify designs for migration.
Distributed Computing
Authors: Rajsbaum Sergio
Published: October 2004

The Distributed Computing Column covers the theory of systems that are composed of a number of interacting computing elements. These include problems of communication and networking, databases, distributed shared memory, multiprocessor architectures, operating systems, verification, internet, and the web.
SEDA
Authors: Welsh Matt , Culler David , Brewer Eric
Published: October 2004

We propose a new design for highly concurrent Internet services, which we call the
staged event-driven architecture
(SEDA). SEDA is intended to support massive concurrency demands and simplify the construction of well-conditioned services. In SEDA, applications consist of a network of event-driven
stages
connected by explicit
queues
. This architecture allows services to be well-conditioned to load, preventing resources from being overcommitted when demand exceeds service capacity. SEDA makes use of a set of
dynamic resource controllers
to keep stages within their operating regime despite large fluctuations in load. We describe several control mechanisms for automatic tuning and load conditioning, including thread pool sizing, event batching, and adaptive load shedding. We present the SEDA design and an implementation of an Internet services platform based on this architecture. We evaluate the use of SEDA through two applications: a high-performance HTTP server and a packet router for the Gnutella peer-to-peer file sharing network. These results show that SEDA applications exhibit higher performance than traditional service designs, and are robust to huge variations in load.
Reprints from Computing Reviews
Authors: Seiferas Joel
Published: October 2004

As a service to our readers,
SIGACT News
has an agreement with
Computing Reviews
to reprint reviews of books and articles of interest to the theoretical computer science community.
Computing Reviews
is a monthly journal that publishes critical reviews on a broad range of computing subjects, including models of computation, formal languages, computational complexity theory, analysis of algorithms, and logics and semantics of programs. ACM members can receive a subscription to
Computing Reviews
for $47 per year by writing to ACM headquarters.
ACM SIGACT News distributed computing column 3
Authors: Rajsbaum Sergio
Published: October 2004

The Distributed Computing Column covers the theory of systems that are composed of a number of interacting computing elements. These include problems of communication and networking, databases, distributed shared memory, multiprocessor architectures, operating systems, verification, internet, and the web.After some announcements, this issue includes a contribution by Idit Keidar and myself.
The finding of thorns
Authors: Kawalek Peter , Wood-Harper Trevor
Published: October 2004

This paper presents a study of a major, multinational program of Enterprise Systems (ES) implementation. The case study subject is a hi-tech manufacturer. The study focuses on the issue of user participation. The investigation inquires into the fact that the implementation method espoused user participation even though the outcome of the project was already known. (Regardless of user input, the ES would be deployed). The paper reports that user participation was deployed to serve the interests of the project manager in reporting local circumstances as the implementation project moved across different sites. The framework for this inquiry was Multiview2, the latest generation of the Multiview information systems (IS) method. The structure of Multiview2 was used as a diagnostic device in order to inquire into the characteristics of the ES method used at the case study sites.
Aggregate traffic performance with active queue management and drop from tail
Authors: Iannaccone Gianluca , May Martin , Diot Christophe
Published: October 2004

Active queue management (AQM) refers to a family of packet dropping mechanisms for router queues that has been proposed to support end-to-end congestion control mechanisms in the Internet. In this paper, we examine the performance of AQM mechanisms by varying two parameters: the queue size and the dropping function. AQM flavors considered include "RED", the more recently proposed "Gentle RED" and an additional mechanism we call "Gentle RED with instantaneous queue size".We use experimentation to analyze the performance of the AQM mechanisms identified above on the aggregate traffic going through a congested router. The metrics used are: TCP goodput, TCP and UDP loss rate, queueing delay and consecutive loss probability. The AQM mechanisms are compared to Drop from Tail, the buffer management mechanism currently found in most operational routers.The major observation is that AQM mechanisms have a minor impact on the aggregate performance metrics we observe. On the other hand, we observe an important sensitivity of the AQMs considered to traffic characteristics that may compromise their operational deployment.
A web server's view of the transport layer
Authors: Allman Mark
Published: October 2004

This paper presents observations of traffic to and from a particular World-Wide Web server over the course a year and a half. This paper presents a longitudinal look at various network path properties, as well as the implementation status of various protocol options and mechanisms. In particular, this paper considers how World-Wide Web clients utilize TCP connections to transfer web data; the deployment of various TCP and HTTP options; the range of round-trip times observed in the network; packet sizes used for WWW transfers; the implications of the measured advertised window sizes; and the impact of using larger initial congestion window sizes. These properties/mechanisms and their implications are explored. An additional goal of this paper is to provide information to help researchers better simulate and emulate realistic networks.
mmdump
Authors: van der Merwe Jacobus , Cáceres Ramón , Chu Yang-hua , Sreenan Cormac
Published: October 2004

Internet multimedia traffic is increasing as applications like streaming media and packet telephony grow in popularity. It is important to monitor the volume and characteristics of this traffic, particularly because its behavior in the face of network congestion differs from that of the currently dominant TCP traffic. To monitor traffic on a high-speed link for extended periods, it is not practical to blindly capture all packets that traverse the link. We present
mmdump
, a tool that parses messages from RTSP, H.323 and similar multimedia session control protocols to set up and tear down packet filters as needed to gather traces of multimedia sessions. Unlike tcpdump, dynamic packet filters are necessary because these protocols dynamically negotiate TCP and UDP port numbers to carry the media content. Our tool captures only packets of interest for optional storage and further analysis, thus greatly reducing resource requirements. This paper presents the design and implementation of
mmdump
and demonstrates its utility in monitoring live RTSP and H.323 traffic on a commercial IP network. The preliminary results obtained from these measurements are presented.
On the validity of digital signatures
Authors: Zhou Jianying , Deng Robert
Published: October 2004

An important feature of digital signatures is to serve as non-repudiation evidence. To be eligible as non-repudiation evidence, a digital signature on an electronic document should remain valid until its expiry date which is specified by some non-repudiation policy. As signature keys may be compromised and the validity of signatures may become questionable, additional security mechanisms need to be imposed on digital signatures. This paper examines the mechanisms for maintaining the validity of digital signatures, and provides a guideline on the use of these mechanisms in various context of applications.
A novel wide-band audio transmission scheme over the Internet with a smooth quality degradation
Authors: Babich Fulvio , Vitez Marko
Published: October 2004

Real-time delivery of multimedia information over the Internet is finding increasing interest. This paper considers wide-band audio transmission utilizing a priority scheme. The proposed scheme complies with both the new Internet Protocol Version 6 (IPv6) and the current Internet Protocol Version 4 (IPv4), providing that, in the latter case, routers are set to manage priority. A new queuing algorithm, namely Priority Weighted Fair Queuing (PWFQ), is defined and evaluated. A scalable audio encoder is adopted to perform audio transmissions over an emulated network. Background traffic is emulated, employing a traffic generator that adopts a self-similar model. Objective and subjective quality tests are performed, using a set of musical excerpts. Quality is evaluated as a function of Internet traffic. In the paper it is shown that, by adopting an encoding technique with scalable bit-rate, and a prioritized transmission algorithm, a smooth degradation of quality may be obtained during network congestion periods. This technique shows better performance than feedback-based algorithms, in which the delayed responses cause the core stage packets to be lost in low-to-high traffic transitions and the enhancement packets not to be transmitted in high-to-low traffic transitions.
TCP rate control
Authors: Karandikar Shrikrishna , Kalyanaraman Shivkumar , Bagal Prasad , Packer Bob
Published: October 2004

This paper presents TCP rate control, a new technique for transparently augmenting end-to-end TCP performance by controlling the sending rate of a TCP source. The sending rate of a TCP source is determined by its window size, the round trip time and the rate of acknowledgments. TCP rate control affects these aspects by modifying the ack number and receiver window fields in acknowledgments and by modulating the acknowledgment rate. From a performance viewpoint a key benefit of TCP rate control is to avoid adverse performance effects due to packet losses such as reduced goodput and unfairness or large spread in per-user goodputs. Further, TCP rate control positively affects performance even if the bottleneck is non-local and the end-host TCP implementations are non-conforming. These aspects are demonstrated through a comparative study of TCP rate control, RED and TCP-ECN. The TCP rate control approach has been implemented and patented by Packeteer Inc.
TCP congestion control with a misbehaving receiver
Authors: Savage Stefan , Cardwell Neal , Wetherall David , Anderson Tom
Published: October 2004

In this paper, we explore the operation of TCP congestion control when the receiver can misbehave, as might occur with a greedy Web client. We first demonstrate that there are simple attacks that allow a misbehaving receiver to drive a standard TCP sender arbitrarily fast, without losing end-to-end reliability. These attacks are widely applicable because they stem from the sender behavior specified in RFC 2581 rather than implementation bugs. We then show that it is possible to modify TCP to eliminate this undesirable behavior entirely, without requiring assumptions of any kind about receiver behavior. This is a strong result: with our solution a receiver can only
reduce
the data transfer rate by misbehaving, thereby eliminating the incentive to do so.
Return link optimization for internet service provision using DVB-S networks
Authors: Samaraweera Nihal K. G.
Published: October 2004

Satellite based Digital Video Broadcasting (DVB-S) allows the same low cost satellite dish to receive both television programs and Internet traffic. The satellite system is used to construct a high-speed simplex distribution system, while the return path, needed for the Internet service will be provided using a low speed terrestrial network. The bandwidth asymmetry between the return and forward paths results in a problem, which we have termed "ACK congestion". A number of techniques that may alleviate ACK congestion over a DVB satellite link are analysed through simulation. The paper also presents a new ACK Compaction technique to eliminate ACK congestion, and an ACK spacing technique to preserve the
self-clocking
principle of TCP.
Program insertion in real-time IP multicasts
Authors: Brassil Jack , Garg Sukesh , Schulzrinne Henning
Published: October 2004

We describe the design, implementation and operation of a prototype system which seamlessly mixes real-time audio and video streams originating from multiple, physically separated sources. Mixing is entirely decentralized, relying on new protocols to coordinate transfer of session control between IP multicast sources. The system is motivated by the desire to perform dynamic insertion of advertisements in active, real-time multimedia sessions. It permits content providers and viewers a far richer collection of relationships, opportunities, and features than possible with traditional broadcast media. Novel system features include 1) spontaneous meetings and business relationships between content providers, 2) program insertions from arbitrary locations on a multicast tree, 3) operation with no modifications to existing software players, 4) audience demographics from Real Time Control Protocol messages, and 5) mechanisms to allow users to select between multiple, simultaneous program transmissions. Additional system applications range from support of emergency broadcasts to the creation of novel
virtual broadcasting networks
.
MPEG transmission schemes for a timed token medium access control network
Authors: Ng Joseph Kee-Yin
Published: October 2004

This paper presents three transmission schemes to improve the transmission of MPEG video over a timed token medium access control (MAC) network. Multiple classes of MPEG video are used in the study. These data are captured from real video programmes and we categorized these video clips according to their traffic burstiness and workload characteristics. The performance measure of the timed token MAC network is in terms of the maximum number of MPEG video streams being transmitted without any frame missing its deadline. This simulation study observed that by employing the Regulated Scheme, we could improve the performance by 28 to 40%. When applying the Grouping Scheme for the MPEG transmission, we can improve the performance between 142 and 149%. When we combined the two schemes together, the Regulated Grouping Scheme can further improve the performance up to 153% which is a dramatic improvement over the original transmission scheme.
A novel approach to mobility management
Authors: Hutchins Ron , Camp Tracy , Enslow Philip H.
Published: October 2004

In this paper, we propose a novel approach to computer mobility. Our approach allows mobility to be rapidly deployed, as the networking infrastructure required for deployment is available off the shelf. Furthermore, a mobile node does not require modifications in order to use these mobile services. While our approach provides rapid deployment and supports both IP and non-IP protocols, only a subset of mobile usage scenarios are offered. In other words, our approach does not solve all the problems of mobility. We discuss the characteristics of mobility usage, and we list the scenarios our approach supports. We believe that the mobile usage scenarios supported by this method are some of the more common usage scenarios. We also believe that investigations into this method will provide more insights into network and mobility research.
Open signaling for ATM, internet and mobile networks (OPENSIG'98)
Authors: Campbell Andrew T. , Katzela Irene , Miki Kazuho , Vicente John
Published: October 2004

The ability to rapidly create and deploy new transport, control and management architectures in response to new service demands is a key factor driving the programmable networking community. Competition between service providers may hinge on the speed at which one provider can respond to new market demands over another. The notion of open programmable networks is having broad impact on service providers and vendors across a range of telecommunication sectors calling for major advances in open network control architecture, network programmability and distributed systems technology. In this paper we discuss the origins of the Open Signalling Working Group (OPENSIG) and present a summary of the fifth Workshop on Open Signaling for ATM, Internet and Mobile Networks (OPENSIG'98), which was held at the University of Toronto, Ontario, October, 1998. We also discuss a number of new initiatives in the area of open programmable networks that have recently emerged.
Secure and efficient key management for dynamic multicast groups
Authors: Park Chang-Seop , Lee Dong-Hoon
Published: October 2004

Proposals for key management of secure multicast that have been published so far are concentrated on reducing the complexity of communication for rekeying. If a group manager controls several multicast application groups and each of them involves a large number of members, it is important to maintain a set of secret keys as small as possible in order to reduce the group manager's storage for key management. In this paper, we propose a tree-based key management scheme, where the group manager can access keys by computing on the fly, without storing them. Using a concept of ID-based key generation and node bits on the tree, a storage for key management by the group manager can be greatly reduced.
New phase 1 exchange mode for IKE framework
Authors: Sierra J. M. , Shepherd S. J.
Published: October 2004

This paper describes some new extensions to the IKE Exchange Mode framework which both simplify the protocol and make each stage of the protocol more efficient. This will allow considerably faster security associations to be accomplished which is critical to system performance in time-limited protocols.
Partial order relations in distributed object environments
Authors: Duchien Laurence , Florin Gérard , Seinturier Lionel
Published: October 2004

We describe several order relations for group cooperative applications. Our goal is to define the main interleaving semantics existing in distributed object environments with group invocations and variable sharing. We generalize the Lamport's
Happened-before
relation defined for message passing applications to a causal relation between actions or methods in object world. Next, we precise a set of order properties for group method invocations. It includes the local, causal and total ordering deduced from the similar ordering in message broadcast protocols, and causally coherent and serializable transactions deduced from the concurrency control. Finally, we present two implementations of one of these order property on distributed object systems GUIDE and CORBA.
Tagged semaphores
Authors: Xu Baowen
Published: October 2004

This paper introduces a new kind of semaphores, i.e., tagged semaphores. Tagged semaphores are the generalization of standard semaphores, and have more powerful describing capability than the latter.
An approach to finding the attacks on the cryptographic protocols
Authors: Sun Yongxing , Wang Xinmei
Published: October 2004

It is necessary to development the formal tools for verifying cryptographic protocols because of the subtlety of cryptographic protocols flaws; In terms of the notions of the restrictive channel and the equivalent message, this paper presents an approach that utilizes the substitution rules of messages and the deduction rules to prove whether the insecure states of the cryptographic protocols are reachable or not, and the analysis of several famous protocols shows the validity of the method.
A top-down operating systems course
Authors: Creak G. Alan , Sheehan Robert
Published: October 2004

We suggest that the conventional course on operating systems, based --- apparently --- on folk memory of an archetypal operating system, could usefully be reorganised to emphasise the importance of the people who use the system, and comment on our experience in designing and presenting such a course.
Overview of TOS
Authors: Nicholas Tyrone , Barchanski Jerzy A.
Published: October 2004

This paper describes TOS - a distributed educational operating system implemented in Java. First, the current trends in commercial operating systems are shortly presented and compared with several available educational operating systems. Next, we give our rationals for Java as the TOS implementation language.. Then the architecture of the system and its components - launchers and servers are described. Finally we explain the advantages of this architecture and provide some information on its implementation and portability.
Scalable hierarchical coarse-grained timers
Authors: Dube Rohit
Published: October 2004

Several network servers and routing and signalling protocols need a large number of events to be scheduled off timers. Some of these applications can withstand a bounded level of inaccuracy in when the timer is scheduled. In this paper we describe a novel mechanism called "
scalable hierarchical coarse grained timers
" which can handle the scheduling of a large number of events while incurring a minimum of cpu and memory overhead. The techniques presented here were implemented on a commercial IP routing system and are used by the routing stack to damp flapping BGP routes. The paper reflects our experiences in carrying out this implementation and the subsequent performance analysis.
Security in mobile agent system
Authors: Kun Yang , Xin Guo , Dayou Liu
Published: October 2004

Despite its many practical benefits, mobile agent technology results in significant new security threats from both malicious agents and hosts. This paper investigates the problems and approaches of mobile agent system, which shows that bi-directional and layered security model may be a good idea to resolve the security problems in mobile agent systems. Other topics about mobile agent security, such as constrained execution and virus detection, are also discussed.
Security issues surrounding programming languages for mobile code
Authors: Gritzalis Stefanos , Aggelis George
Published: October 2004

JAVA is claimed to be a system programming language having a number of advantages over traditional programming languages. These advantages stem from the fact that it is a platform - independent language, thus promising truly network oriented computing as long as a nearly universal system for distributing applications. On the other hand, although being an interpreted, much simpler, scripting language, Safe-Tcl was proposed as an executable contents type of MIME and thus as the standard language for executable contents within email. Consequently, both languages claim to be suitable for transmitting executable content over the Internet, in other words manipulating mobile code. However, the ability to download, integrate, and execute code from a remote computer raises serious concerns about JAVA's as well as Safe-Tcl's effect on network security. In this paper, the potential security risks of mobile code are discussed, a brief introduction to both programming languages is given, and the details of each of the proposed security mechanisms are presented. Finally a comparison of the two security models is given, centered upon the efficiency and flexibility of current implementations as well as upcoming extensions.
The control devolution
Authors: Hanseth Ole , Ciborra Claudio U. , Braa Kristin
Published: October 2004

When looking at the implementation of ERP systems in large organizations, the typical business concerns are attaining the goals of the application, usually globalization and efficiency, securing the organization's acceptance, avoiding rigidity, and so on. By now, the literature is full of both normative models on how to implement ERPs successfully and cautioning tales of how the road to success is paved by traps, slowdowns, and even disillusion. This paper does not take sides in this emerging literature, simply because it submits that there is a need to look at the broader context of ERP implementations.There is a need to discover new meanings before turning to consulting or critique. Such meanings stem from reconsidering the managerial concepts that accompany ERP implementation, especially the issues of "what is an ERP," how to achieve strategic alignment, and what globalization really entails. The authors frame the study of ERP in organizations within the broader context of an analysis of the consequences of modernity. The new vocabulary sheds a different light on what organizations are doing with ERP: these systems are open, pasted-up, uncontrollable expanding infrastructures; strategic alignment flounders in never-ending tactics and compromises; globalization generates side effects. Harnessed to enhance control over complex, global organizations, ERPs enshrine the consequences of modernity in a nutshell: they accelerate organizational drift and runaway. The case of the introduction of SAP in a large Norwegian company illustrates a range of drifting processes and side effects.
ERP project dynamics and enacted dialogue
Authors: Besson Patrick , Rowe Frantz
Published: October 2004

Different views on change and IT- related outcomes have been proposed in the literature. Most privilege the technological deterministic and organizational imperative positions. This article introduces two types of process views on change arising from designers' inability to forecast the impacts of ERP on work and governance:• a dialectical process due to the lack of perceived leeway by the actors, and• a teleological process view, where actors feel they have more leeway and where they try to take advantage of technological effects that they feel they can controlBuilding on the concept of enactment and on the nature of conflicts, this work demonstrates the necessity to articulate these views in a theoretical framework describing the dynamics of ERP projects.This framework is employed to interpret problems arising from ERP choice and implementation in the French context. During the "chartering phase," the deterministic vision dominates the perceptions of designers. During the "project phase," the designers come closer to the organizational imperative view when they customize the system and make integration/differentiation choices. During the "shakedown" and subsequent phases, organizational outcomes are often not realized because of job and governance conflicts with end users.
Extending the technology acceptance model
Authors: Mathieson Kieran , Peacock Eileen , Chin Wynne W.
Published: October 2004

There has been considerable research on the factors that predict whether individuals will accept and voluntarily use information systems. The technology acceptance model (TAM) has a base in psychological research, is parsimonious, explains usage behavior quite well, and can be operationalized with valid and reliable instruments. A limitation of TAM is that it assumes usage is volitional, that is, there are no barriers that would prevent an individual from using an IS if he or she chose to do so. This research extends TAM by adding perceived user resources to the model, with careful attention to placing the construct in TAM's existing nomological structure. In contrast to measures of self-efficacy and perceived behavioral control that concentrate on how well individuals perceive they can execute specific courses of action, this paper examines perceptions of adequate resources that can facilitate or inhibit such behaviors. The inclusion of both a formative and reflective set of measures provides the opportunity for the researcher and manager to decide whether to evaluate only the overall perceptions of adequate resources or also the specific underlying causes. The extended model incorporating these measures was then tested in the field. The results confirmed that perceived user resources is a valuable addition to the model.
Three challenges for IS
Authors: Gray Paul
Published: October 2004

The purpose of this article is to discuss three challenges that face the IS academic community. Specifically, these challenges are:• Keeping up• Remote learning• Electronic publishingThese three challenges were selected because they are little discussed in our field, yet they are interrelated and they affect most of the readers of
DATA BASE.
Of course, they are not the only challenges the IS field faces. However, others such as, for example, electronic commerce are well discussed elsewhere.In this article, we first examine each of the three challenges and discuss how they affect the IS academic profession and IS practice. We then discuss what IS professionals can do to meet them and what they will gain as a field by resolving them.
Invitation to a public debate on ethical computer use
Authors: Conger Sue , Loch Karen D.
Published: October 2004

To obtain ethically defensible behavior in a particular situation, or context, one must first define what is considered ethically defensible in that context. Without contextual norms, people assume no norms and are then (mis)guided solely by their own experience. According to Integrated Social Contracts Theory, typical contexts include individual-only situations and situations in which the individual is a member of professional, business and social organizations. Norm development is a complex process. It requires discussion between many individuals to identify the ethical issues relevant to each context, to define ethically defensible behaviors for each, and then to decide which norms take priority in the event of a conflict. This paper argues that the importance of context identifies fundamental flaws in the notion that professional associations can address all ethical behaviors through generic codes of ethics. The arguement goes further to assert that Integrated Social Contracts Theory, if applied to universal codes of ethics, can facilitate their redefinition into a useful set of guidelines for ethical professional behavior.
Information ethics in a responsibility vacuum
Authors: Linderman James L. , Schiano William T.
Published: October 2004

The authors start with the premise that the field of information technology is not a "profession," because it is missing some of the defining characteristics of a profession. In particular, the authors claim the field is impotent in terms of certification and meaningful sanctions for unprofessional behavior. Furthermore, unlike "true" professions, leadership (with the frequent exception of IT in academia) is more often than not in hands of someone who has not come "up through the ranks" and therefore does not enjoy peer status.Handicapped by lack of credentialing, the inability to deal effectively with unprofessional behavior, and non-peer leadership, the resulting power vacuum has led to a responsibility vacuum, which in turn complicates issues of information ethics.The authors then argue that the IT field, whatever it considers itself to be, or is perceived by society to be, has a responsibility to society to disclose its position on ethical issues: to proclaim or disclaim such positions if there is consensus or acknowledge disagreement within the field in the absence of consensus. Specifically, there arises as societal obligation to "own up" to the realities of our not being a profession and such implications as our inability to deal with unprofessional behavior.The authors conclude that information ethicists must not only assist the field in identifying ethical issues and formulating appropriate positions, but they must also lobby the field regarding the importance of keeping society informed on the existence, non-existence, or evolution of such positions; and directly alert society, on behalf of the field, to the existence, non-existence, or evolution of such positions. In particular, the authors assert that any progress the field can make in resolving ethical jurisdiction---who gets to have say in matters of information ethics---will have an immense positive impact on the future of information ethics, contribute significantly to progress in matters of legal jurisdiction, and may even assist the field in resolving its identity.