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1.
Global transaction support for workflow management systems: from formal specification to practical implementation 总被引:6,自引:0,他引:6
Paul Grefen Jochem Vonk Peter Apers 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(4):316-333
In this paper, we present an approach to global transaction management in workflow environments. The transaction mechanism
is based on the well-known notion of compensation, but extended to deal with both arbitrary process structures to allow cycles
in processes and safepoints to allow partial compensation of processes. We present a formal specification of the transaction
model and transaction management algorithms in set and graph theory, providing clear, unambiguous transaction semantics. The
specification is straightforwardly mapped to a modular architecture, the implementation of which is first applied in a testing
environment, then in the prototype of a commercial workflow management system. The modular nature of the resulting system
allows easy distribution using middleware technology. The path from abstract semantics specification to concrete, real-world
implementation of a workflow transaction mechanism is thus covered in a complete and coherent fashion. As such, this paper
provides a complete framework for the application of well-founded transactional workflows.
Received: 16 November 1999 / Accepted 29 August 2001 Published online: 6 November 2001 相似文献
2.
工作流管理系统异常处理的方法与层次 总被引:1,自引:0,他引:1
工作流技术在信息处理领域的应用越来越受到重视,但应用中环境和用户要求的不断发展和变化需要工作流管理系统具有灵活的处理能力,工作流系统的异常处理正是要解决这种不断要求的变化。文章介绍了工作流异常处理的应用范围,总结了不同的应用方法,从系统的角度提出了工作流未来的异常处理层次,并在研究可适应性工作流技术方面进行了探讨。 相似文献
3.
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
4.
Due to the complex nature of scientific workflow environments, temporal violations often take place and may severely reduce the timeliness of the execution's results. To handle temporal violations in an automatic and cost-effective fashion, two interdependent fundamental issues viz. the definition of fine-grained recoverable temporal violations and the design of light-weight effective exception handling strategies need to be resolved. However, most existing works study them separately without defining a comprehensive framework. To address such a problem, with the probability based temporal consistency model which defines the range of recoverable temporal violations, a novel general automatic and cost-effective exception handling framework is proposed in this paper where fine-grained temporal violations are defined based on the empirical function for the capability lower bounds of the exception handling strategies. To serve as a representative case study, a concrete example exception handling framework which consists of three levels of fine-grained temporal violations and their corresponding exception handling strategies is presented. The effectiveness of the example framework is evaluated by large scale simulation experiments conducted in the SwinDeW-G scientific grid workflow system. The experimental results demonstrate that the example framework can significantly reduce the overall average violation rates of local temporal constraints and global temporal constraints to 0.127% and 0.167% respectively. 相似文献
5.
Building knowledge base management systems 总被引:1,自引:0,他引:1
John Mylopoulos Vinay Chaudhri Dimitris Plexousakis Adel Shrufi Thodoros Topologlou 《The VLDB Journal The International Journal on Very Large Data Bases》1996,5(4):238-263
Advanced applications in fields such as CAD, software engineering, real-time process control, corporate repositories and digital
libraries require the construction, efficient access and management of large, shared knowledge bases. Such knowledge bases
cannot be built using existing tools such as expert system shells, because these do not scale up, nor can they be built in
terms of existing database technology, because such technology does not support the rich representational structure and inference
mechanisms required for knowledge-based systems. This paper proposes a generic architecture for a knowledge base management
system intended for such applications. The architecture assumes an object-oriented knowledge representation language with
an assertional sublanguage used to express constraints and rules. It also provides for general-purpose deductive inference
and special-purpose temporal reasoning. Results reported in the paper address several knowledge base management issues. For
storage management, a new method is proposed for generating a logical schema for a given knowledge base. Query processing
algorithms are offered for semantic and physical query optimization, along with an enhanced cost model for query cost estimation.
On concurrency control, the paper describes a novel concurrency control policy which takes advantage of knowledge base structure
and is shown to outperform two-phase locking for highly structured knowledge bases and update-intensive transactions. Finally,
algorithms for compilation and efficient processing of constraints and rules during knowledge base operations are described.
The paper describes original results, including novel data structures and algorithms, as well as preliminary performance evaluation
data. Based on these results, we conclude that knowledge base management systems which can accommodate large knowledge bases
are feasible.
Edited by Gunter Schlageter and H.-J. Schek.
Received May 19, 1994 / Revised May 26, 1995 / Accepted September 18, 1995 相似文献
6.
A reference model for team-enabled workflow management systems 总被引:15,自引:0,他引:15
Today's workflow systems assume that each work item is executed by a single worker. From the viewpoint of the system, a worker with the proper qualifications selects a work item, executes the associated work, and reports the result. There is usually no support for teams, i.e., groups of people collaborating by jointly executing work items (e.g., the program committee of a conference, the management team of a company, a working group, and the board of directors). In this paper, we propose the addition of a team concept to today's workflow management systems. Clearly, this involves a marriage of workflow and groupware technology. To shed light on the introduction of teams, we extend the traditional organizational meta model with teams and propose a team-enabled workflow reference model. For this reference model and to express constraints with respect to the distribution of work to teams, we use object constraint language (OCL). 相似文献
7.
Multimedia systems must be able to support a certain quality of service (QoS) to satisfy the stringent real-time performance
requirements of their applications. HeiRAT, the Heidelberg Resource Administration Technique, is a comprehensive QoS management
system that was designed and implemented in connection with a distributed multimedia platform for networked PCs and workstations.
HeiRAT includes techniques for QoS negotiation, QoS calculation, resource reservation, and resource scheduling for local and
network resources. 相似文献
8.
Denise J. Ecklund Vera Goebel Thomas Plagemann Earl F. Ecklund Jr. 《Multimedia Systems》2002,8(5):431-442
In this paper, we present a separable, reusable middleware solution that provides coordinated, end-to-end QoS management
over any type of service component, and can use existing (legacy) QoS management solutions (by using wrappers) in a distributed
multimedia system. Our middleware solution incorporates strategic and tactical QoS managers, and supports protocols and messages
between tactical managers and managed application components, and between QoS managers in the management hierarchy. Strategic
QoS managers take a global view of QoS provided by a set of application components within the manager's policy domain. Tactical
QoS managers provide local control over application components. We introduce the concept of QoS policy domains to scope the
authority of a strategic QoS manager. We describe how the management hierarchy is dynamically configured and reconfigured
based on runtime needs of the application. 相似文献
9.
K. Selçuk Candan Eric Lemar V.S. Subrahmanian 《The VLDB Journal The International Journal on Very Large Data Bases》2000,9(2):131-153
Abstract. Though there has been extensive work on multimedia databases in the last few years, there is no prevailing notion of a multimedia
view, nor there are techniques to create, manage, and maintain such views. Visualizing the results of a dynamic multimedia
query or materializing a dynamic multimedia view corresponds to assembling and delivering an interactive multimedia presentation
in accordance with the visualization specifications. In this paper, we suggest that a non-interactive multimedia presentation
is a set of virtual objects with associated spatial and temporal presentation constraints. A virtual object is either an object, or the result of a query.
As queries may have different answers at different points in time, scheduling the presentation of such objects is nontrivial.
We then develop a probabilistic model of interactive multimedia presentations, extending the non-interactive model described
earlier. We also develop a probabilistic model of interactive visualization where the probabilities reflect the user profiles,
or the likelihood of certain user interactions. Based on this probabilistic model, we develop three utility-theoretic based
types of prefetching algorithms that anticipate how users will interact with the presentation. These prefetching algorithms
allow efficient visualization of the query results in accordance with the underlying specification. We have built a prototype
system that incorporates these algorithms. We report on the results of experiments conducted on top of this implementation.
Received June 10, 1998 / Accepted November 10, 1999 相似文献
10.
In a multimedia server, multiple media streams are generally serviced in a cyclic fashion. Due to non-uniform playback rates
and asynchronous arrivals of queries, there tends to be spare disk bandwidth in each service cycle. In this paper, we study
the issue of dynamically using spare disk bandwidth and buffer to maximize the system throughput of a multimedia server. We
introduce the concept of minimizing buffer consumption as the criterion to select an appropriate media stream to utilize the spare system resources. Buffer consumption measures
not only the amount of buffer but also the amount of time such buffer space is occupied (i.e., the space-time product). Different
alternatives to utilizing spare disk bandwidth are examined, including different rate-adjustable retrievals of an already
activated stream and prefetching the next waiting stream. For rate-adjustable retrievals, we study buffer consumption-based and remaining-time-based criteria for selecting an active stream to increase retrievals. Simulations are conducted to evaluate and compare different
cases. The results show that (1) minimizing buffer consumption is the right criterion for maximizing the system throughput
with spare disk bandwidth; (2) in general, prefetching a waiting stream incurs more buffer consumption, and thus is less effective
than rate-adjustable retrieval of active streams in maximizing the system throughput; and (3) the advantage of rate-adjustable
retrieval over prefetching is especially significant when service cycle time is small. 相似文献
11.
Concurrency control in hierarchical multidatabase systems 总被引:1,自引:0,他引:1
Sharad Mehrotra Henry F. Korth Avi Silberschatz 《The VLDB Journal The International Journal on Very Large Data Bases》1997,6(2):152-172
Over the past decade, significant research has been done towards developing transaction management algorithms for multidatabase
systems. Most of this work assumes a monolithic architecture of the multidatabase system with a single software module that
follows a single transaction management algorithm to ensure the consistency of data stored in the local databases. This monolithic
architecture is not appropriate in a multidatabase environment where the system spans multiple different organizations that
are distributed over various geographically distant locations. In this paper, we propose an alternative multidatabase transaction
management architecture, where the system is hierarchical in nature. Hierarchical architecture has consequences on the design
of transaction management algorithms. An implication of the architecture is that the transaction management algorithms followed
by a multidatabase system must be composable– that is, it must be possible to incorporate individual multidatabase systems as elements in a larger multidatabase system.
We present a hierarchical architecture for a multidatabase environment and develop techniques for concurrency control in such
systems.
Edited by R. Sacks-Davis. Received June 27, 1994 / Accepted September 26, 1995 相似文献
12.
提出了一种基于虚拟组织集成框架IFVO的工作流管理系统的异常处理机制,深入分析了工作流系统异常处理的相关问题,并结合实例阐述了该机制的实现和应用。 相似文献
13.
Semantic integrity support in SQL:1999 and commercial (object-)relational database management systems 总被引:1,自引:0,他引:1
Can Türker Michael Gertz 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(4):241-269
The correctness of the data managed by database systems is vital to any application that utilizes data for business, research,
and decision-making purposes. To guard databases against erroneous data not reflecting real-world data or business rules,
semantic integrity constraints can be specified during database design. Current commercial database management systems provide
various means to implement mechanisms to enforce semantic integrity constraints at database run-time.
In this paper, we give an overview of the semantic integrity support in the most recent SQL-standard SQL:1999, and we show
to what extent the different concepts and language constructs proposed in this standard can be found in major commercial (object-)relational
database management systems. In addition, we discuss general design guidelines that point out how the semantic integrity features
provided by these systems should be utilized in order to implement an effective integrity enforcing subsystem for a database.
Received: 14 August 2000 / Accepted: 9 March 2001 / Published online: 7 June 2001 相似文献
14.
Workflow Requirements Modelling Using XML 总被引:2,自引:0,他引:2
When modelling inter-organisational workflow it is important not to make assumptions such as with regard to the formats of
the data exchanged between the workflow participants or the technical infrastructures and platforms, as they can restrict
the range of possible workflow management implementations. The approach presented in this paper allows for the conceptual
modelling of workflow processes using primitive constructs such as nodes, rules and business documents. The paper presents
both a graphical notation for modelling workflows as well as a mapping of the workflow constructs to XML models that follows
the Workflow Management Coalition interoperability standards. This allows the modelled workflow to be interpreted and executed
by a variety of workflow engines. 相似文献
15.
Managing database server performance to meet QoS requirements in electronic commerce systems 总被引:1,自引:0,他引:1
Patrick Martin Wendy Powley Hoi-Ying Li Keri Romanufa 《International Journal on Digital Libraries》2002,3(4):316-324
The performance of electronic commerce systems has a major impact on their acceptability to users. Different users also demand
different levels of performance from the system, that is, they will have different Quality of Service (QoS) requirements. Electronic commerce systems are the integration of several different types of servers and each server must
contribute to meeting the QoS demands of the users. In this paper we focus on the role, and the performance, of a database server within an electronic commerce system.
We examine the characteristics of the workload placed on a database server by an electronic commerce system and suggest a
range of QoS requirements for the database server based on this analysis of the workload. We argue that a database server
must be able to dynamically reallocate its resources in order to meet the QoS requirements of different transactions as the
workload changes. We describe Quartermaster, which is a system to support dynamic goal-oriented resource management in database
management systems, and discuss how it can be used to help meet the QoS requirements of the electronic commerce database server.
We provide an example of the use of Quartermaster that illustrates how the dynamic reallocation of memory resources can be
used to meet the QoS requirements of a set of transactions similar to transactions found in an electronic commerce workload.
We briefly describe the memory reallocation algorithms used by Quartermaster and present experiments to show the impact of
the reallocations on the performance of the transactions.
Published online: 22 August 2001 相似文献
16.
Secure buffering in firm real-time database systems 总被引:2,自引:0,他引:2
Binto George Jayant R. Haritsa 《The VLDB Journal The International Journal on Very Large Data Bases》2000,8(3-4):178-198
Many real-time database applications arise in electronic financial services, safety-critical installations and military systems
where enforcing security is crucial to the success of the enterprise. We investigate here the performance implications, in terms of killed transactions,
of guaranteeing multi-level secrecy in a real-time database system supporting applications with firm deadlines. In particular, we focus on the buffer management aspects of this issue.
Our main contributions are the following. First, we identify the importance and difficulties of providing secure buffer management
in the real-time database environment. Second, we present SABRE, a novel buffer management algorithm that provides covert-channel-free security. SABRE employs a fully dynamic one-copy allocation policy for efficient usage of buffer resources. It also incorporates
several optimizations for reducing the overall number of killed transactions and for decreasing the unfairness in the distribution
of killed transactions across security levels. Third, using a detailed simulation model, the real-time performance of SABRE
is evaluated against unsecure conventional and real-time buffer management policies for a variety of security-classified transaction
workloads and system configurations. Our experiments show that SABRE provides security with only a modest drop in real-time
performance. Finally, we evaluate SABRE's performance when augmented with the GUARD adaptive admission control policy. Our
experiments show that this combination provides close to ideal fairness for real-time applications that can tolerate covert-channel
bandwidths of up to one bit per second (a limit specified in military standards).
Received March 1, 1999 / Accepted October 1, 1999 相似文献
17.
Scott D. Stoller 《Distributed Computing》2000,13(2):85-98
Summary. This paper proposes a framework for detecting global state predicates in systems of processes with approximately-synchronized
real-time clocks. Timestamps from these clocks are used to define two orderings on events: “definitely occurred before” and
“possibly occurred before”. These orderings lead naturally to definitions of 3 distinct detection modalities, i.e., 3 meanings of “predicate held during a computation”, namely: (“ possibly held”), (“ definitely held”), and (“ definitely held in a specific global state”). This paper defines these modalities and gives efficient algorithms for detecting
them. The algorithms are based on algorithms of Garg and Waldecker, Alagar and Venkatesan, Cooper and Marzullo, and Fromentin
and Raynal. Complexity analysis shows that under reasonable assumptions, these real-time-clock-based detection algorithms
are less expensive than detection algorithms based on Lamport's happened-before ordering. Sample applications are given to
illustrate the benefits of this approach.
Received: January 1999 / Accepted: November 1999 相似文献
18.
Integrating computer-based information into the real world of the user is becoming a crucial challenge for the designers of
interactive systems. The Augmented Reality (AR) paradigm illustrates this trend. Information is provided by an AR system to
facilitate or to enrich the natural way in which the user interacts with the real environment. We focus on the output of such
systems and, in particular, on the smooth integration of additional information in the real environment of the user. We characterize
the integration of the computer-provided entities with the real ones using two new properties: compatibility and continuity.
After defining the two properties, we provide factors and an analytical method needed for assessing them. We also empirically
study the two properties to highlight their impact on interaction. The CASPER system, developed in our teams, is used to illustrate
the discussion.
Published online: 14 May 2002 相似文献
19.
Alberto Bartoli Gianluca Dini Lanfranco Lopriore 《International Journal on Software Tools for Technology Transfer (STTT)》2001,3(2):235-245
With reference to a memory management system supporting the single address space abstraction and a uniform, persistent view
of storage, we present a set of mechanisms that allow applications to exert explicit control over memory management activities.
These mechanisms make it possible to move the contents of a virtual page to primary memory for fast processor access, or to
push these contents back to secondary memory to free primary memory space. Our memory management scheme allows programs to
exploit the memory reference pattern of the underlying algorithms, thereby improving utilisation of the system storage resources.
This result is illustrated by using significant examples of memory management activities implemented at the application program
level.
Published online: 8 February 2001 相似文献
20.
As the number of video streams to be supported by a digital video delivery system (DVDS) increases, an improved understanding
of the necessity for reliable and cost-efficient support for a considerable number of video streams (in the magnitude of tens
of thousands), and the dependency largely on software capabilities emerges. Even in the presence of an optimal hardware configuration,
or model, and associated costs, using software to exploit the underlying hardware capabilities is of paramount importance.
Although a number of DVDSs have become operational, their ability to deliver the required services mainly depends on the small
number of streams supported and the hardware trade-offs. It is imperative that current software developments account for
the eventual scalability of the number of video streams without commensurate increase in hardware. In this paper, we present
strategies for the management of video streams in order to maintain and satisfy their space and time requirements. We use
a DVDS architectural model with functionally dichotomized nodes: a single-node partition is responsible for data retrieval,
while the remaining partition of nodes accepts user requests, determines object locations, and routes requests through the
network that connects both partitions. We present a detailed analysis of the issues related to queuing I/O requests and data
buffering. The discussion includes the requirements for arranging and scheduling I/O requests and data buffers, with the objective
of guaranteeing the required data availability rates for continuous media display. 相似文献