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951.
Chiang Lee Chi-Sheng Shih Yaw-Huei Chen 《The VLDB Journal The International Journal on Very Large Data Bases》2001,9(4):327-343
Traditional algorithms for optimizing the execution order of joins are no more valid when selections and projections involve
methods and become very expensive operations. Selections and projections could be even more costly than joins such that they
are pulled above joins, rather than pushed down in a query tree. In this paper, we take a fundamental look at how to approach
query optimization from a top-down design perspective, rather than trying to force one model to fit into another. We present
a graph model which is designed to characterize execution plans. Each edge and each vertex of the graph is assigned a weight
to model execution plans. We also design algorithms that use these weights to optimize the execution order of operations.
A cost model of these algorithms is developed. Experiments are conducted on the basis of this cost model. The results show
that our algorithms are superior to similar work proposed in the literature.
Received 20 April 1999 / Accepted 9 August 2000 Published online 20 April 2001 相似文献
952.
German Shegalov Michael Gillmann Gerhard Weikum 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(1):91-103
Advanced e-services require efficient, flexible, and easy-to-use workflow technology that integrates well with mainstream
Internet technologies such as XML and Web servers. This paper discusses an XML-enabled architecture for distributed workflow
management that is implemented in the latest version of our Mentor-lite prototype system. The key asset of this architecture
is an XML mediator that handles the exchange of business and flow control data between workflow and business-object servers
on the one hand and client activities on the other via XML messages over http. Our implementation of the mediator has made
use of Oracle's XSQL servlet. The major benefit of the advocated architecture is that it provides seamless integration of
client applications into e-service workflows with scalable efficiency and very little explicit coding, in contrast to an earlier,
Java-based, version of our Mentor-lite prototype that required much more code and exhibited potential performance problems.
Received: 30 October 2000 / Accepted: 19 December 2000 Published online: 27 April 2001 相似文献
953.
An Internet-based negotiation server for e-commerce 总被引:6,自引:0,他引:6
Stanley Y.W. Su Chunbo Huang Joachim Hammer Yihua Huang Haifei Li Liu Wang Youzhong Liu Charnyote Pluempitiwiriyawej Minsoo Lee Herman Lam 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(1):72-90
This paper describes the design and implementation of a replicable, Internet-based negotiation server for conducting bargaining-type
negotiations between enterprises involved in e-commerce and e-business. Enterprises can be buyers and sellers of products/services
or participants of a complex supply chain engaged in purchasing, planning, and scheduling. Multiple copies of our server can
be installed to complement the services of Web servers. Each enterprise can install or select a trusted negotiation server
to represent his/her interests. Web-based GUI tools are used during the build-time registration process to specify the requirements,
constraints, and rules that represent negotiation policies and strategies, preference scoring of different data conditions,
and aggregation methods for deriving a global cost-benefit score for the item(s) under negotiation. The registration information
is used by the negotiation servers to automatically conduct bargaining type negotiations on behalf of their clients. In this
paper, we present the architecture of our implementation as well as a framework for automated negotiations, and describe a
number of communication primitives which are used in the underlying negotiation protocol. A constraint satisfaction processor
(CSP) is used to evaluate a negotiation proposal or counterproposal against the registered requirements and constraints of
a client company. In case of a constraint violation, an event is posted to trigger the execution of negotiation strategic
rules, which either automatically relax the violated constraint, ask for human intervention, invoke an application, or perform
other remedial operations. An Event-Trigger-Rule (ETR) server is used to manage events, triggers, and rules. Negotiation strategic
rules can be added or modified at run-time. A cost-benefit analysis component is used to perform quantitative analysis of
alternatives. The use of negotiation servers to conduct automated negotiation has been demonstrated in the context of an integrated
supply chain scenario.
Received: 30 October 2000 / Accepted: 12 January 2001 Published online: 2 August 2001 相似文献
954.
Massimo Mecella Barbara Pernici 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(1):2-15
Component-based approaches are becoming more and more popular to support Internet-based application development. Different
component modeling approaches, however, can be adopted, obtaining different abstraction levels (either conceptual or operational).
In this paper we present a component-based architecture for the design of e-applications, and discuss the concept of wrapper
components as building blocks for the development of e-services, where these services are based on legacy systems. We discuss
their characteristics and their applicability in Internet-based application development.
Received: 30 October 2000 / Accepted: 9 January 2001 Published online: 28 June 2001 相似文献
955.
A survey of approaches to automatic schema matching 总被引:76,自引:1,他引:75
Erhard Rahm Philip A. Bernstein 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(4):334-350
Schema matching is a basic problem in many database application domains, such as data integration, E-business, data warehousing,
and semantic query processing. In current implementations, schema matching is typically performed manually, which has significant
limitations. On the other hand, previous research papers have proposed many techniques to achieve a partial automation of
the match operation for specific application domains. We present a taxonomy that covers many of these existing approaches,
and we describe the approaches in some detail. In particular, we distinguish between schema-level and instance-level, element-level
and structure-level, and language-based and constraint-based matchers. Based on our classification we review some previous
match implementations thereby indicating which part of the solution space they cover. We intend our taxonomy and review of
past work to be useful when comparing different approaches to schema matching, when developing a new match algorithm, and
when implementing a schema matching component.
Received: 5 February 2001 / Accepted: 6 September 2001 Published online: 21 November 2001 相似文献
956.
Carlo Combi Giuseppe Pozzi 《The VLDB Journal The International Journal on Very Large Data Bases》2001,9(4):294-311
The granularity of given temporal information is the level of abstraction at which information is expressed. Different units of measure allow
one to represent different granularities. Indeterminacy is often present in temporal information given at different granularities:
temporal indeterminacy is related to incomplete knowledge of when the considered fact happened. Focusing on temporal databases, different granularities
and indeterminacy have to be considered in expressing valid time, i.e., the time at which the information is true in the modeled
reality. In this paper, we propose HMAP (The term is the transliteration of an ancient Greek poetical word meaning “day”.), a temporal data model extending the capability
of defining valid times with different granularity and/or with indeterminacy. In HMAP, absolute intervals are explicitly represented by their start,end, and duration: in this way, we can represent valid times as “in December 1998 for five hours”, “from July 1995, for 15 days”, “from March
1997 to October 15, 1997, between 6 and 6:30 p.m.”. HMAP is based on a three-valued logic, for managing uncertainty in temporal relationships. Formulas involving different temporal
relationships between intervals, instants, and durations can be defined, allowing one to query the database with different
granularities, not necessarily related to that of data. In this paper, we also discuss the complexity of algorithms, allowing
us to evaluate HMAP formulas, and show that the formulas can be expressed as constraint networks falling into the class of simple temporal problems,
which can be solved in polynomial time.
Received 6 August 1998 / Accepted 13 July 2000 Published online: 13 February 2001 相似文献
957.
D. Laurent J. Lechtenbörger N. Spyratos G. Vossen 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(4):295-315
Views over databases have regained attention in the context of data warehouses, which are seen as materialized views. In this setting, efficient view maintenance is an important issue, for which the notion of self-maintainability has been identified as desirable. In this paper, we extend the concept of self-maintainability to (query and update) independence within a formal framework, where independence with respect to arbitrary given sets of queries and updates over the sources
can be guaranteed. To this end we establish an intuitively appealing connection between warehouse independence and view complements. Moreover, we study special kinds of complements, namely monotonic complements, and show how to compute minimal ones in the presence of keys and foreign keys in the underlying databases. Taking advantage
of these complements, an algorithmic approach is proposed for the specification of independent warehouses with respect to
given sets of queries and updates.
Received: 21 November 2000 / Accepted: 1 May 2001 Published online: 6 September 2001 相似文献
958.
Constraint-based deductive model checking 总被引:2,自引:0,他引:2
Giorgio Delzanno Andreas Podelski 《International Journal on Software Tools for Technology Transfer (STTT)》2001,3(3):250-270
We show that constraint logic programming (CLP) can serve as a conceptual basis and as a practical implementation platform
for the model checking of infinite-state systems. CLP programs are logical formulas (built up from constraints) that have
both a logical interpretation and an operational semantics. Our contributions are: (1) a translation of concurrent systems
(imperative programs) into CLP programs with the same operational semantics; and (2) a deductive method for verifying safety
and liveness properties of the systems which is based on the logical interpretation of the CLP programs produced by the translation.
We have implemented the method in a CLP system and verified well-known examples of infinite-state programs over integers,
using linear constraints here as opposed to Presburger arithmetic as in previous solutions.
Published online: 18 July 2001 相似文献
959.
960.
Hon-Son Don 《International Journal on Document Analysis and Recognition》2001,4(2):131-138
A new thresholding method, called the noise attribute thresholding method (NAT), for document image binarization is presented
in this paper. This method utilizes the noise attribute features extracted from the images to make the selection of threshold
values for image thresholding. These features are based on the properties of noise in the images and are independent of the
strength of the signals (objects and background) in the image. A simple noise model is given to explain these noise properties.
The NAT method has been applied to the problem of removing text and figures printed on the back of the paper. Conventional
global thresholding methods cannot solve this kind of problem satisfactorily. Experimental results show that the NAT method
is very effective.
Received July 05, 1999 / Revised July 07, 2000 相似文献