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Australasian Conference on computer Human Interaction

作者： G. Fitzpatrick T. Mansfield S.M. Kaplan Department Computer Science University of Queensland QLD Australia CRC for Distributed Systems Technology University of Queensland Australia

We believe that virtual simulation of physical environments is an insufficient basis for building collaborative support systems. In response, we present a locales framework which frames collaboration as the interaction of individuals within social worlds regardless of whether that interaction is physical or virtual. The overview describes the five aspects of the framework: locale foundations, where locales are the basic structures providing the affordances for the work of social worlds; mutuality in interaction, including presence and awareness issues; individual views of multiple locales of interest, defined by the individual's participation in multiple social worlds; interaction trajectories, capturing the temporal dimensions of interaction; and civic structures, which embed locales and the collaborative work of groups in the larger public sphere.

关键词： Collaboration Collaborative work Sociology Appropriate technology Psychology Software design Bridges Humans Employment Bonding

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Verification problems in conceptual workflow specifications

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15th International Conference on Conceptual Modeling, ER 1996

作者： Ter Hofstede, A.H.M. Orlowska, M.E. Rajapakse, J. Department of Computer Science University of Queensland Brisbane Qld 4072 Australia Distributed Systems Technology Centre University of Queensland BrisbaneQld 4072 Australia

ISBN: (纸本)9783540617846

Most of today's business requirements can only be accomplished through integration of various autonomous systems which were initially designed to serve the needs of particular applications. In the literature workfiows are proposed to design these kinds of applications. The key tool for designing such applications is a powerful conceptual specification language. Such a language should be capable of capturing interactions and cooperation between component tasks of workflows among others. These include sequential execution, iteration, choice, parallelism and synchronisation. The central focus of this paper is the verification of such process control aspects in conceptual workflow specifications. As it is generally agreed upon that the later in the software development process an error is detected, the more it will cost to correct it, it is of vital importance to detect errors as early as possible in the systems development process. In this paper some typical verification problems in worldlow specifications are identified and their complexity is addressed. It will be proven that some fundamental problems are not tractable and we will show what restriction is needed to allow termination problems to be recognized in polynomial time.

关键词： Specification languages

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An overview of catalog design problems in resource discovery

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INTERNET RESEARCH-ELECTRONIC NETWORKING APPLICATIONS AND POLICY 1996年第1期6卷 33-&页

作者： Goodchild, A Andrew Goodchild is a PhD student at the Department of Computer Science University of Queensland QLD 4072 Australia. Tel: +61 7 3365 4209 Fax: +61 7 3365 1999 E‐mail: andrewg@cs.uq.oz.au . He is also affiliated as a Student with the Distributed Systems Technology Centre DSTC and the Research Data Network Collaborative Research Centre RDN‐CRC

Discusses some of the problems designers face in building catalogs in large networks and relates them back to the resource discovery problem. Currently many catalogs tend to be built in an ad hoc fashion-which leads to a great variety in the quality of publicly accessible network catalogs. Furthermore, the research surrounding these catalogs tends to focus on narrow technical issues-resulting in difficult-to-use catalogs. Addresses this problem by providing a usability framework based on the library science and human computer interaction literature, and demonstrates some of those principles via an example of a prototype. Results are interesting to resource discovery tool developers in that a framework for understanding the general resource discovery problem is provided and some techniques for dealing with those problems are presented.

关键词： design and development information retrieval interfaces resources

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Physical spaces, virtual places and social worlds: a study of work in the virtual 96

Physical spaces, virtual places and social worlds: a study o...

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Proceedings of the 1996 ACM conference on computer supported cooperative work

作者： Geraldine Fitzpatrick Simon Kaplan Tim Mansfield Dept. of Computer Science University of Queensland Queensland Australia 4072 Depts. of Computer Science University of Queensland & University of Illinois at Urbana-Champaign CRC for Distributed Systems Technology University of Queensland Queensland Australia 4072

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CORRECTNESS ISSUES FOR distributed RELATIONAL DATABASE DESIGN

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distributed AND PARALLEL DATABASES 1995年第4期3卷 361-380页

作者： SHARMA, NP EWALD, CA CRC for Distributed Systems Technology Department of Computer Science The University of Queensland Brisbane Australia

This paper examines correctness issues that arise in distributed database design. A distributed relational database design is traditionally considered to be valid if every global relation can be reconstructed from its fragments by join operations. In this paper, three successively less restrictive definitions of validity are presented, each providing progressively improved handling of incomplete information. Examining these forms, a hybrid reconstruction approach involving inner- and outer-joins is proposed and we briefly describe its application to query formulation. We also propose replacing the notion of global reconstructability with the less restrictive, yet intuitively natural notion of object reconstructability. Universal relations need not be constructed. The need for maintenance of constraints across sites of a distributed system is discussed, and the notion of a distributed referential constraint is proposed which fulfills this need.

关键词： distributed DATABASES DESIGN CORRECTNESS INCOMPLETE INFORMATION CONSTRAINT PRESERVATION QUERY CORRECTNESS

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EVALUATING MULTIPLE JOIN QUERIES IN A distributed DATABASE SYSTEM

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MATHEMATICAL AND computer MODELLING 1995年第7期21卷 83-98页

作者： REID, DJ Distributed Systems Technology Centre Department of Computer Science The University of Queensland St. Lucia Queensland 4072 Australia

It is proposed that the execution of a set of join queries in a distributed environment should be considered cooperatively, rather than as a set of separate requests. With this understanding, a model of multiple query execution in the form of a linear integer program is offered. Several requests are issued to the distributed database management system, each specifying the collation of information comprised of a number of logically distinct data sets, or relations, and dispersed across the sites of a distributed system. Performing these tasks demands the usage of limited resources, so that efficient management commands the smallest additional imposition possible. Both processors and the data communication devices that interconnect them are exploited;an optimal strategy is defined to be one that minimizes a weighted sum of the costs of computation and those of information exchange incurred in resolving the group of queries. Previous models of join query evaluation would regard each individual query in isolation, to produce a sequence of independent execution strategies, one correspondingly for every request. By instead permitting multiple utilization of intermediate computations, any overlap between these queries can be exploited to further reduce the total demand placed on the system as a whole. Through investigations into the character of a number of interacting join computations, performed at a single site in isolation, an earlier single query model [1] can be extended to facilitate the cooperative execution of an entire group.

关键词： distributed DATABASE SYSTEM INTEGER PROGRAM JOIN QUERY RELATIONAL DATABASE

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EXECUTING JOIN QUERIES IN AN UNCERTAIN distributed ENVIRONMENT

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MATHEMATICAL AND computer MODELLING 1995年第3期22卷 9-23页

作者： REID, DJ Distributed Systems Technology Centre Department of Computer Science The University of Queensland St. Lucia Queensland 4072 Australia

The uncertainty inherent in the distributed environment poses new challenges to the efficient utilization of system resources in managing database transactions. In response to this realization, the execution of a join query in a system with probabilistic resource and cost parameters is contemplated, leading to the development of stochastic programming models. Information in the form of relational tables and scattered amongst the sites of a distributed database system is to be collated and presented to the appropriate user, in response to an issued request. Performing this task demands the usage of limited resources;the ultimate goal is the determination of an execution strategy incurring minimal cost to the system. The actual state of any network component at the moment of its exploitation cannot be exactly ascertained in advance. Any interrogation of a distant element must be communicated by the network, and this involves a delay, as perceived by the questioner, during which the state of the system may change. Indeed, the time at which a task assigned to any particular component cannot itself be precisely predicted, even if the future state of the component could be known definitively. By considering the uncertain nature of the distributed environment, the earlier model of join query evaluation presented in [1] can be modified in different ways to account for system parameters known only in a stochastic sense. This new level of subjectivity is a revelation of the many different attitudes that may be taken towards the chance of infeasibility in the solution, for the major issue in dealing with uncertainty is the choice of an appropriate measure of risk.

关键词： distributed DATABASE SYSTEM INTEGER PROGRAMMING JOIN QUERY RELATIONAL DATABASE STOCHASTIC PROGRAMMING

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Comments on soviet encryption algorithm

Comments on soviet encryption algorithm

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Workshop on the Theory and Application of Cryptographic Techniques, EUROCRYPT 1994

作者： Chames, C. O’Connor, L. Pieprzyk, J. Safavi-Naini, R. Zheng, Y. Department of Computer Science University of Wollongong WollongongNSW Australia Distributed Systems Technology Center Queensland University of Technology BrisbaneQLD Australia

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Associative broadcast communication in massively parallel SIMD machines: a practical approach

Associative broadcast communication in massively parallel SI...

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IEEE International Conference on Algorithms and Architectures for Parallel Processing (ICAP)

作者： O.-H. Cho R.M. Colomb CRC for Distributed Systems Technology Department of Computer Science University of Queensland Brisbane QLD Australia

In massively parallel SIMD machines, communication bottlenecks have been a major problem due to the limitation of available topologies. Especially they are not well suited to broadcast-type communications. Some suggested approaches are not practical, even though they are asymptotically fast, because they incur large minimum latency. In this paper, a simple and practical linear broadcast-type communication algorithm which is based on associative computing and does not use interconnection networks at all, is presented.< >

关键词： Broadcasting Delay Cyclic redundancy check computer science Topology computer networks Multiprocessor interconnection networks Algebra distributed computing

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PARALLEL AND distributed TLM COMPUTATION WITH SIGNAL-PROCESSING FOR ELECTROMAGNETIC-FIELD MODELING

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INTERNATIONAL JOURNAL OF NUMERICAL MODELLING-ELECTRONIC NETWORKS DEVICES AND FIELDS 1995年第3-4期8卷 169-185页

作者： SO, PPM ESWARAPPA, C HOEFER, WJR NSERC/MPR Teltech Research Chair in RF Engineering Department of Electrical and Computer Engineering University of Victoria Victoria British Columbia V8W 3P6 Canada Poman So received his B.Sc. degree in computer science and physics from the University of Toronto Toronto Onatario Canada in 1985. He obtained his B.A. Sc. and M.A.Sc. degrees in electrical engineering (summa cum laude) from the University of Ottawa Ottawa Ontario Canada in 1987 and 1989 respectively. Mr So was a research engineer in the University of Ottawa from January 1989 to October 1991 his research interests included CAD techniques of microwave circuits and numerical methods for electromagnetic wave modelling. He specialized in the development of electromagnetic engineering CAD software and successfully implemented a number of electromagnetic wave simulators based on the two-dimensional and three-dimensional transmission-line matrix methods. From August 1990 to February 1991 he accompanied Professor W. J. R. Hoefer to Rome Italy and Sophia Antiopolas France. During that time he implemented a parallel version of the 3D-TLM simulator for the CM-2 Connection Machine using C-Star and X Windows Library. He is a research engineer and a Ph.D. student at the University of Victoria Victoria British Columbia Canada. He ported the 2D- and 3D-TLM simulators to DECmpp 1200 massively parallel computer using MPL C and C++. He also combined OSA90/hope a commercially available microwave CAD program with a 2D-TLM simulation module for geometry optimization using the Datapipe technique of OSA90/hope. Recently he has developed a distributed client-server computing technique for the TLM method this technique could accelerate the TLM simulation by more than an order of magnitude. Channabasappa Eswarappa received the M.Tech. degree in electrical engineering from the Indian Institute of Technology Kanpur India in 1983 and Ph. D. degree from the University of Ottawa Canada in 1990. He worked as an Assistant Executive Engineer and later as

This paper describes the implementation of transmission-line matrix (TLM) method algorithms on a massively parallel computer (DECmpp 12000), the technique of distributed computing in the UNIX environment, and the combination of TLM analysis with Prony's method as well as with autoregressive moving average (ARMA) digital signal processing for electromagnetic field modelling. By combining these advanced computation techniques, typical electromagnetic field modelling of microwave structures by TLM analysis can be accelerated by a few orders of magnitude.

关键词： Mathematical models

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