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International Conference on Data engineering

作者： H.A. Kuno E.A. Rundensteiner Department of Elect. Engineering and Computer Science Software Systems Research Laboratory University of Michigan Ann Arbor MI USA

View materialization is known to be a valuable technique for performance optimization in relational databases, and much work has been done addressing the problem of consistently maintaining relational views under update operations. However, little progress has been made thus far regarding the topic of view materialization in object-oriented databases (OODBs). In this paper, we demonstrate that there are several significant differences between the relational and object-oriented paradigms that can be exploited when addressing the object-oriented view materialization problem. We use the subsumption relationships between classes to identify branches of classes to which we do not need to propagate updates. Similarly, we use encapsulated interfaces combined with the fact that any unique database property is inherited from a single location to provide a "registration/notification" service for optimizing incremental view updates. We also report results from the experimental studies we have run on the MultiView system measuring the impact of these optimization strategies.

关键词： Object oriented modeling Relational databases Object oriented databases computer science software systems Laboratories Optimization Programming profession NASA Prototypes

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Augmented inherited multi-index structure for maintenance of materialized path query views

Augmented inherited multi-index structure for maintenance of...

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International Workshop on research Issues in Data engineering

作者： H.A. Kuno E.A. Rundensteiner Department of Elect. Engineering and Computer Science Software Systems Research Laboratory University of Michigan Ann Arbor MI USA

Materialized complex object-oriented views are a promising technique for the integration of heterogeneous databases and the development of powerful data warehousing systems. Path query views are virtual classes formed from selection queries that specify a predicate upon the value of an aggregation hierarchy path. The primary difference between previous work regarding OODB indexing and the efficient implementation of materialized path query views addressed in this paper lies in the nature of their usage. For OODB indexing, query usage is the primary purpose of index structures. Because the materialized view data itself can be used to answer queries, the primary use of index structures with regard to materialized path query views is for the incremental maintenance of views in the face of updates. We have developed an augmented inherited multi-index (AIM) strategy that is specifically tailored for the maintenance of materialized path query views. We find that we can improve update performance by augmenting traditional inherited multi-indices with structured representations of the path queries that use them. This enables us to use class hierarchy relationships to prune the number of aggregation paths that must be re-instantiated during update propagation and also to support complex path queries that include cycles.

关键词： Object oriented databases Warehousing Indexing Distributed databases Workflow management software computer science software systems Laboratories Information technology Database systems

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Consistent view removal in transparent schema evolution systems

Consistent view removal in transparent schema evolution syst...

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International Workshop on research Issues in Data engineering

作者： V. Crestana-Taube E.A. Rundensteiner Department of Elect. Engineering and Computer Science Software Systems Research Laboratory University of Michigan Ann Arbor MI USA

We have developed the transparent schema evolution (TSE) system that, simulating schema evolution using object-oriented views, allows for the interoperability of applications with diverse and even changing requirements. TSE relieves users of the risk of making existing application programs obsolete when run against the modified schema, because the old view schema is maintained while a new view schema is generated to capture the changes desired by the user. However TSE may be generating a large number of schema versions (object-oriented view schemata) over time, resulting in an excessive build-up of classes and underlying object instances-some of which may potentially no longer be in use. We propose to solve this problem by developing techniques for effective and consistent schema removal. First, we characterize four potential problems of schema consistency that could be caused by removal of a single virtual class; and then outline our solution approach for each of these problems. Second, we demonstrate that view schema removal is sensitive to the order in which individual classes are processed. Our solution to this problem is the development of a dependency graph model for capturing the class relationships, used as a foundation for selecting among removal sequences. Designed to optimize the performance of the TSE system by effective schema version removal, the proposed techniques will enable more effective interoperability among evolving software applications.

关键词： Application software Object oriented modeling computer science software systems Laboratories Computational modeling Marine vehicles Design optimization software performance Veins

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Improved scheduling algorithms for minsum criteria 23rd

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23rd International Colloquium on Automata, Languages, and Programming, ICALP 1996

作者： Chakrabarti, Soumen Phillips, Cynthia A. Schulz, Andreas S. Shmoys, David B. Stein, Cliff Wein, Joel Computer Science Division U.C. BerkeleyCA94720 United States Sandia National Labs AlbuquerqueNM United States Department of Mathematics Technical University of Berlin Berlin10623 Germany School of Operations Research and Industrial Engineering Cornell University IthacaNY14853 United States Department of Computer Science Sudikoff Laboratory Dartmouth College HanoverNH United States Department of Computer Science Polytechnic University BrooklynNY11201 United States

ISBN: (纸本)3540614400

We consider the problem of finding near-optimal solutions for a variety of MV-haid scheduling problems for which the objective is to minimize the total weighted completion time. Recent work has led to the development of several techniques that yield constant worst-case bounds in a number of settings. We continue this line of research by providing improved performance guarantees for several of the most basic scheduling models, and by giving the first constant performance guarantee for a number of more realistically constrained scheduling problems. For example, we give an improved performance guarantee for minimizing the total weighted completion time subject to release dates on a single machine, and subject to release dates and/or precedence constraints on identical parallel machines. We also give improved bounds on the power of preemption in scheduling jobs with release dates on parallel machines. We give improved on-line algorithms for many more realistic scheduling models, including environments with parallelizable jobs, jobs contending for shared resources, tree precedence-constrained jobs, as well as shop scheduling models. In several of these cases, we give the first constant performance guarantee achieved on-line. Finally, one of the consequences of our work is the surprising structural property that there are schedules that simultaneously approximate the optimal makespan and the optimal weighted completion time to within small constants. Not only do such schedules exist, but we can find approximations to them with an on-line algorithm. © Springer-Verlag Berlin Heidelberg 1996.

关键词： Scheduling algorithms

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Virtual memory versus file interfaces for large, memory-intensive scientific applications 96

Virtual memory versus file interfaces for large, memory-inte...

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Proceedings of the 1996 ACM/IEEE conference on Supercomputing

作者： Yoonho Park Ridgway Scott Stuart Sechrest High Performance Computing Center University of Houston Houston TX Software Systems Research Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI

ISBN: (纸本)9780897918541

Scientific applications often require some strategy for temporary data storage to do the largest possible simulations. The use of virtual memory for temporary data storage has received criticism because of performance problems. However, modern virtual memory found in recent operating systems such as Cenju-3/DE give application writers control over virtual memory policies. We demonstrate that custom virtual memory policies can dramatically reduce virtual memory overhead and allow applications to run out-of-core efficiently. We also demonstrate that the main advantage of virtual memory, namely programming simplicity, is not lost.

关键词： custom policies

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Simultaneous speech segmentation and phoneme recognition using dynamic programming

Simultaneous speech segmentation and phoneme recognition usi...

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： R.S. Bajwa R.M. Owens T.P. Kelliher Semiconductor Research Laboratory Hitachi America Limited San Jose CA USA Department of Computer Science & Engineering Pennsylvania State University University Park PA USA Department of Mathematics and Computer Science Westminster College New Wilmington PA USA

In this paper a dynamic programming algorithm for simultaneous speech segmentation and phoneme recognition is presented. Given a sequence of samples of an unknown speech pattern and a library of phonemes, this algorithm finds the best phonological match and, with a backtracking step, identifies the phoneme boundaries. This approach is different from a traditional two step process whereby first the phoneme boundaries are determined locally and then speech recognition is performed. Its advantage over the two step process is that incorrect phoneme boundaries due to slurring or sudden changes in the speech are reduced. Unlike other dynamic programming algorithms, it does not lend itself to systolic wavefront processing, hence an alternate parallel algorithm is presented.

关键词： Speech recognition Dynamic programming Libraries Speech analysis Heuristic algorithms computer science Pattern matching Laboratories mathematics Educational institutions

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Virtual Memory versus File Interface for Large, Memory-Intensive Scientific Applications

Virtual Memory versus File Interface for Large, Memory-Inten...

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Supercomputing Conference

作者： Yoonho Park R. Scott S. Sechrest High performance computing center University of Houston Houston TX USA Software Systems Research Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

关键词： Memory Operating systems Control systems

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Quantitive studies of data-locality sensitivity on the EARTH multithreaded architecture: preliminary results

Quantitive studies of data-locality sensitivity on the EARTH...

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International Conference on High Performance Computing

作者： Xin-Min Tian S. Nemawarkar G.R. Gao H. Hum O. Maquelin A. Sodan K. Theobald IBM Toronto Software Laboratory Toronto Canada Department of Electrical Engineering McGill University Montreal Canada School of Computer Science McGill University Montreal Canada Intel Corporation Portland USA GMD FIRST Research Center Berlin Germany

Multithreading has been promoted as an effective mechanism to hide inter-processor communications and remote data access latencies by quickly switching among a set of ready threads. In this paper, we show that multitreading provides an immunity to the performance variations due to changes in data distributions in a distributed-memory multiprocessor. First, toe propose two performance metrics to quantify the sensitivity of performance to data-locality. Second, we perform a quantitative comparison of data-locality sensitivity with both single-threaded and multithreaded computations. These experiments are performed on a 20-node EARTH-MANNA system. Our results show that not only does a multithreaded computation yields higher performance than the single-threaded version, but also that its performance is more robust (less affected) by variations in data-locality.

关键词： Earth Yarn Multithreading Delay Distributed computing High performance computing computer architecture Communication switching Benchmark testing Laboratories

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PROGRAM VIEW GENERATION AND CHANGE ANALYSIS USING ATTRIBUTED DEPENDENCY GRAPHS

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JOURNAL OF software MAINTENANCE-research AND PRACTICE 1995年第4期7卷 239-261页

作者： ALZOUBI, R PRAKASH, A Software Systems Research Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122 U.S.A. He is currently an Assistant Professor at Yarmouk University Irbed H.K. of Jordan. Earlier he has worked for the Ford Motor Company in Dearborn Michigan. His research interests are in the area of software engineering. Since 1989 he has been with the Department of Electrical Engineering and Computer Science at the University of Michigan Ann Arbor where he is currently an Associate Professor. His research interests include software engineering and computer-supported cooperative work. He is a member of the ACM and the IEEE Computer Society.

software maintenance is usually the most expensive phase of the software life-cycle, Program understanding and impact-of-change analysis are two of the major activities during this phase, In this paper, we describe attributed program dependency graphs (APDGs), a model to store information derived from the program source code and ease construction of tools for software maintenance, We show how the model can be used for interactive view generation and doing two kinds of impact-of-change analysis-incremental and comparison-oriented. Incremental change analysis uses APDGs and a Rule Base to provide a way for the user to analysis the effect of proposed well-defined changes, Comparison-oriented change analysis allows a user to generate structural semantic differences between two versions of a subsystem after an arbitrary sequence of changes, We also introduce SCAN, a prototype collection of loosely integrated tools based on the APDG model and describe our experiences with the system.

关键词： PROGRAM REPRESENTATION DEPENDENCY GRAPHS PROGRAM UNDERSTANDING REVERSE-engineering REengineering IMPACT ANALYSIS CHANGE ANALYSIS

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Supporting the evolution of design artifacts with representations of context and intent 95

Supporting the evolution of design artifacts with representa...

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1st Conference on Designing Interactive Systems: Processes, Practices, Methods, and Techniques, DIS 1995

作者： Fischer, Gerhard Nakakoji, Kumiyo Ostwald, Jonathan Department of Computer Science and Institute of Cognitive Science University of Colorado BoulderCO80309-0430 United States Software Engineering Laboratory Software Research Associ. Inc. 1-1-1 Hirakawa-cho Chiyoda-ku Tokyo102 Japan

ISBN: (纸本)0897916735

The design of complex artifacts is essentially an evolutionary process that requires collaboration among stakeholders. Domain-oriented design environments (DODEs) support the evolution of artifacts both by individual designers and by designers participating in longterm, indirect collaboration. DODEs provide representations for generic and specific levels of context. This context supports individual designers by making the information space relevant to the current design intent, and longterm collaboration among designers by allowing them to ground their communication around design artifacts. We demonstrate our approach using the KID (Knowing-inDesign) system, articulate principles for representations of context and intent, and discuss various approaches to represent intent and context in design environments. © 1995 ACM.

关键词： Knowledge based systems

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