共查询到20条相似文献,搜索用时 15 毫秒
1.
R. Braumandl M. Keidl A. Kemper D. Kossmann A. Kreutz S. Seltzsam K. Stocker 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(1):48-71
We present the design of ObjectGlobe, a distributed and open query processor for Internet data sources. Today, data is published
on the Internet via Web servers which have, if at all, very localized query processing capabilities. The goal of the ObjectGlobe
project is to establish an open marketplace in which data and query processing capabilities can be distributed and used by any kind of Internet application. Furthermore, ObjectGlobe integrates cycle providers (i.e., machines) which carry out query processing operators. The overall picture is to make it possible to execute a query
with – in principle – unrelated query operators, cycle providers, and data sources. Such an infrastructure can serve as enabling
technology for scalable e-commerce applications, e.g., B2B and B2C market places, to be able to integrate data and data processing
operations of a large number of participants. One of the main challenges in the design of such an open system is to ensure
privacy and security. We discuss the ObjectGlobe security requirements, show how basic components such as the optimizer and
runtime system need to be extended, and present the results of performance experiments that assess the additional cost for
secure distributed query processing. Another challenge is quality of service management so that users can constrain the costs
and running times of their queries.
Received: 30 October 2000 / Accepted: 14 March 2001 Published online: 7 June 2001 相似文献
2.
Fabio Casati Maria Grazia Fugini Isabelle Mirbel Barbara Pernici 《Requirements Engineering》2002,7(2):73-106
Workflow management systems are becoming a relevant support for a large class of business applications, and many workflow
models as well as commercial products are currently available. While the large availability of tools facilitates the development
and the fulfilment of customer requirements, workflow application development still requires methodological guidelines that
drive the developers in the complex task of rapidly producing effective applications. In fact, it is necessary to identify
and model the business processes, to design the interfaces towards existing cooperating systems, and to manage implementation
aspects in an integrated way. This paper presents the WIRES methodology for developing workflow applications under a uniform
modelling paradigm – UML modelling tools with some extensions – that covers all the life cycle of these applications: from
conceptual analysis to implementation. High-level analysis is performed under different perspectives, including a business and an organisational perspective. Distribution, interoperability and cooperation with external information systems are considered in this early
stage. A set of “workflowability” criteria is provided in order to identify which candidate processes are suited to be implemented
as workflows. Non-functional requirements receive particular emphasis in that they are among the most important criteria for
deciding whether workflow technology can be actually useful for implementing the business process at hand. The design phase
tackles aspects of concurrency and cooperation, distributed transactions and exception handling. Reuse of component workflows,
available in a repository as workflow fragments, is a distinguishing feature of the method. Implementation aspects are presented
in terms of rules that guide in the selection of a commercial workflow management system suitable for supporting the designed
processes, coupled with guidelines for mapping the designed workflows onto the model offered by the selected system. 相似文献
3.
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
4.
Stefan Deßloch Theo Härder Nelson Mattos Bernhard Mitschang Joachim Thomas 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(2):79-95
The increasing power of modern computers is steadily opening up new application domains for advanced data processing such
as engineering and knowledge-based applications. To meet their requirements, concepts for advanced data management have been
investigated during the last decade, especially in the field of object orientation. Over the last couple of years, the database
group at the University of Kaiserslautern has been developing such an advanced database system, the KRISYS prototype. In this
article, we report on the results and experiences obtained in the course of this project. The primary objective for the first
version of KRISYS was to provide semantic features, such as an expressive data model, a set-oriented query language, deductive
as well as active capabilities. The first KRISYS prototype became completely operational in 1989. To evaluate its features
and to stabilize its functionality, we started to develop several applications with the system. These experiences marked the
starting point for an overall redesign of KRISYS. Major goals were to tune KRISYS and its query-processing facilities to a
suitable client/server environment, as well as to provide elaborate mechanisms for consistency control comprising semantic
integrity constraints, multi-user synchronization, and failure recovery. The essential aspects of the resulting client/server
architecture are embodied by the client-side data management needed to effectively support advanced applications and to gain
the required system performance for interactive work. The project stages of KRISYS properly reflect the essential developments
that have taken place in the research on advanced database systems over the last years. Hence, the subsequent discussions
will bring up a number of important aspects with regard to advanced data processing that are of significant general importance,
as well as of general applicability to database systems.
Received June 18, 1996 / Accepted November 11, 1997 相似文献
5.
Oscar Díaz Arturo Jaime 《The VLDB Journal The International Journal on Very Large Data Bases》1997,6(4):282-295
Active database management systems (DBMSs) are a fast-growing area of research, mainly due to the large number of applications
which can benefit from this active dimension. These applications are far from being homogeneous, requiring different kinds
of functionalities. However, most of the active DBMSs described in the literature only provide a fixed, hard-wired execution model to support the active dimension. In object-oriented DBMSs, event-condition-action rules have been propo
sed for providing active behaviour. This paper presents EXACT, a rule manager for object-oriented DBMSs which provides a variety
of options from which the designer can choose the one that best fits the semantics of the concept to be supported by rules.
Due to the difficulty of foreseeing future requirements, special attention has been paid to making rule management easily
extensible, so that the user can tailor it to suit specific applications. This has been borne out by an implementation in
ADAM, an object
-oriented DBMS. An example is shown of how the default mechanism can be easily extended to support new requirements.
Edited by Y. Vassiliou. Received May 26, 1994 / Revised January 26, 1995, June 22, 1996 / Accepted November 4, 1996 相似文献
6.
Gabriel Taubin 《The Visual computer》2002,18(5-6):357-367
inverse subdivision algorithms , with linear time and space complexity, to detect and reconstruct uniform Loop, Catmull–Clark, and Doo–Sabin subdivision
structure in irregular triangular, quadrilateral, and polygonal meshes. We consider two main applications for these algorithms.
The first one is to enable interactive modeling systems that support uniform subdivision surfaces to use popular interchange
file formats which do not preserve the subdivision structure, such as VRML, without loss of information. The second application
is to improve the compression efficiency of existing lossless connectivity compression schemes, by optimally compressing meshes
with Loop subdivision connectivity. Our Loop inverse subdivision algorithm is based on global connectivity properties of the
covering mesh, a concept motivated by the covering surface from Algebraic Topology. Although the same approach can be used for other subdivision schemes, such as Catmull–Clark, we
present a Catmull–Clark inverse subdivision algorithm based on a much simpler graph-coloring algorithm and a Doo–Sabin inverse
subdivision algorithm based on properties of the dual mesh. Straightforward extensions of these approaches to other popular
uniform subdivision schemes are also discussed.
Published online: 3 July 2002 相似文献
7.
8.
Integration – supporting multiple application classes with heterogeneous performance requirements – is an emerging trend
in networks, file systems, and operating systems. We evaluate two architectural alternatives – partitioned and integrated
– for designing next-generation file systems. Whereas a partitioned server employs a separate file system for each application
class, an integrated file server multiplexes its resources among all application classes; we evaluate the performance of the
two architectures with respect to sharing of disk bandwidth among the application classes. We show that although the problem
of sharing disk bandwidth in integrated file systems is conceptually similar to that of sharing network link bandwidth in
integrated services networks, the arguments that demonstrate the superiority of integrated services networks over separate
networks are not applicable to file systems. Furthermore, we show that: an integrated server outperforms the partitioned server
in a large operating region and has slightly worse performance in the remaining region; the capacity of an integrated server
is larger than that of the partitioned server; and an integrated server outperforms the partitioned server by a factor of
up to 6 in the presence of bursty workloads. 相似文献
9.
10.
Anat Eyal Tova Milo 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(1):16-38
A broad spectrum of electronic commerce applications is currently available on the Web, providing services in almost any
area one can think of. As the number and variety of such applications grow, more business opportunities emerge for providing
new services based on the integration and customization of existing applications. (Web shopping malls and support for comparative
shopping are just a couple of examples.) Unfortunately, the diversity of applications in each specific domain and the disparity
of interfaces, application flows, actor roles in the business transaction, and data formats, renders the integration and manipulation
of applications a rather difficult task. In this paper we present the Application Manifold system, aimed at simplifying the intricate task of integration and customization of e-commerce applications. The scope of
the work in this paper is limited to web-enabled e-commerce applications. We do not support the integration/customization
of proprietary/legacy applications. The wrapping of such applications as web services is complementary to our work. Based
on the emerging Web data standard, XML, and application modeling standard, UML, the system offers a novel declarative specification
language for describing the integration/customization task, supporting a modular approach where new applications can be added
and integrated at will with minimal effort. Then, acting as an application generator, the system generates a full integrated/customized
e-commerce application, with the declarativity of the specification allowing for the optimization and verification of the
generated application. The integration here deals with the full profile of the given e-commerce applications: the various
services offered by the applications, the activities and roles of the different actors participating in the application (e.g.,
customers, vendors), the application flow, as well as with the data involved in the process. This is in contrast to previous
works on Web data integration that focused primarily on querying the data available in the applications, mostly ignoring the
additional aspects mentioned above.
Received: 30 October 2000 / Accepted 14 March 2001 Published online: 2 August 2001 相似文献
11.
Effective timestamping in databases 总被引:3,自引:0,他引:3
Kristian Torp Christian S. Jensen Richard T. Snodgrass 《The VLDB Journal The International Journal on Very Large Data Bases》2000,8(3-4):267-288
Many existing database applications place various timestamps on their data, rendering temporal values such as dates and times
prevalent in database tables. During the past two decades, several dozen temporal data models have appeared, all with timestamps
being integral components. The models have used timestamps for encoding two specific temporal aspects of database facts, namely
transaction time, when the facts are current in the database, and valid time, when the facts are true in the modeled reality.
However, with few exceptions, the assignment of timestamp values has been considered only in the context of individual modification
statements.
This paper takes the next logical step: It considers the use of timestamping for capturing transaction and valid time in the
context of transactions. The paper initially identifies and analyzes several problems with straightforward timestamping, then
proceeds to propose a variety of techniques aimed at solving these problems. Timestamping the results of a transaction with
the commit time of the transaction is a promising approach. The paper studies how this timestamping may be done using a spectrum
of techniques. While many database facts are valid until now, the current time, this value is absent from the existing temporal types. Techniques that address this problem using different
substitute values are presented. Using a stratum architecture, the performance of the different proposed techniques are studied.
Although querying and modifying time-varying data is accompanied by a number of subtle problems, we present a comprehensive
approach that provides application programmers with simple, consistent, and efficient support for modifying bitemporal databases
in the context of user transactions.
Received: March 11, 1998 / Accepted July 27, 1999 相似文献
12.
A new algorithm for clipping a line segment against a pyramid in E
3 is presented. This algorithm avoids computation of intersection points that are not end points of the output line segment.
It also solves all cases more effectively. The performance of this algorithm is shown to be consistently better than that
of existing algorithms, including the Cohen–Sutherland, Liang–Barsky, and Cyrus–Beck algorithms. 相似文献
13.
E. Panagos A. Biliris 《The VLDB Journal The International Journal on Very Large Data Bases》1997,6(3):209-223
Client-server object-oriented database management systems differ significantly from traditional centralized systems in terms
of their architecture and the applications they target. In this paper, we present the client-server architecture of the EOS
storage manager and we describe the concurrency control and recovery mechanisms it employs. EOS offers a semi-optimistic locking
scheme based on the multi-granularity two-version two-phase locking protocol. Under this scheme, multiple concurrent readers
are allowed to access a data item while it is being updated by a single writer. Recovery is based on write-ahead redo-only
logging. Log records are generated at the clients and they are shipped to the server during normal execution and at transaction
commit. Transaction rollback is fast because there are no updates that have to be undone, and recovery from system crashes
requires only one scan of the log for installing the changes made by transactions that committed before the crash. We also
present a preliminary performance evaluation of the implementation of the above mechanisms.
Edited by R. King. Received July 1993 / Accepted May 1996 相似文献
14.
Many computer applications today require some form of distributed computing to allow different software components to communicate. Several different commercial products now exist based on the Common Object Request Broker Architecture (CORBA) of the Object Management Group. The use of such tools, however, often requires the modification of existing systems, rather than the development of new applications. The objective of this research has been to integrate the use of a CORBA tool into an existing engineering design application for the purpose of (1) evaluating the amount of re‐engineering that is involved to effectively integrate distributed object computing into an existing application, and (2) evaluating the use and performance of distributed object computing in an engineering domain, which often requires the transfer of large amounts of information. The results of this work demonstrate that CORBA technology can be easily integrated into existing applications. The ease of the integration as well as the efficiency of the resulting system, however, depends upon the degree of modification that developers are willing to consider in the re‐engineering process. The most transparent approach to the use of CORBA requires less modification and generally produces less efficient performance. The less transparent approach to the use of CORBA can potentially require significant system modification but produce greater performance gains. This work outlines issues that must be considered for the partitioning of functionality between the client and the server, development of an IDL interface, development of client and server‐side wrappers, and support for concurrent, multi‐user access. In addition, this work also provides performance and implementation comparisons of different techniques for the use of wrappers and for the transfer of large data files between the client and the server. Performance comparisons for the incorporation of concurrent access are also presented. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
15.
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
16.
Alex Aizman 《International Journal on Software Tools for Technology Transfer (STTT)》2001,3(4):456-468
Advances in technology raise expectations. As far as software engineering is concerned, the common expectation is that coding
and deploying applications is going to be simple. It seems, though, that software engineering is not getting easier, and the
complexity moves to an application domain. One of the sources of complexity is an application concurrency. It is not an uncommon
development practice that concurrency and transaction management in multi-user, multi-threaded, event-driven applications
are postponed until after most of the required functionality is implemented. This situation has various explanations. On the
one hand, business logic may require access and modification of large sets of inter-connected application objects. On the
other, testing and stress-testing of this logic becomes possible only at advanced stages of product development. At these
stages, increasing lock granularities may appear to be less "expensive" than debugging race conditions and deadlocks. Coarse-grained
locking has, of course, an adverse effect on application scalability.
Declaring rules of concurrency outside of the application may solve part of the problem. This paper presents an approach allowing
developers to define concurrency in application-specific terms, design it in the early stages of development, and implement
it using a documented API of the concurrency engine (CE). Simple notation makes it possible to record concurrency specifications in terms of application operations, relationships between application resources, and synchronization conflicts between operations. These concepts are demonstrated on examples. The final sections include the CE UML diagram, notes on API usage, and performance
benchmarks.
Published online: 25 July 2001 相似文献
17.
The problem of an instructive and realistic animation and visualization of the shadow- and color-conditions during conjunctions
of actively and passively illuminated cosmic objects has found only particularly satisfying solutions so far. As an example
we study a total solar eclipse. There are didactic shortcomings of specialized astronomical software, even though solutions
have been given, which are very impressive for experts.
Using the possibilities of commercial 3D-animation software we give an object-oriented partial solution. In order to get correct
astronomical representations we model – for different tasks – the object space under cinematic aspects with parameters for
spatial and temporal scaling, for illumination and coloring under couplings of varying strength. The adaptation of the parameters
to optimal acceptance of the spectator must be done a posteriori. 相似文献
18.
Joseph F. McCarthy 《Personal and Ubiquitous Computing》2001,5(1):75-77
Most environments are passive– deaf, dumb and blind, unaware of their inhabitants and unable to assist them in a meaningful way. However, with the advent
of ubiquitous computing – ever smaller, cheaper and faster computational devices embedded in a growing variety of “smart”
objects – it is becoming increasingly possible to create active environments: physical spaces that can sense and respond appropriately to the people and activities taking place within them.
Most of the early ubiquitous computing applications focus on how individuals interact with their environments as they work on foreground tasks. In contrast, this paper focuses on how groups of people affect and are affected by background aspects of their environments. 相似文献
19.
Location is one of the most important elements of context in ubiquitous computing. In this paper we describe a location model, a spatial-aware communication model and an implementation of the models that exploit location for processing and communicating context. The location model presented describes a location
tree, which contains human-readable semantic and geometric information about an organisation and a structure to describe the
current location of an object or a context. The proposed system is dedicated to work not only on more powerful devices like
handhelds, but also on small computer systems that are embedded into everyday artefact (making them a digital artefact). Model and design decisions were made on the basis of experiences from three prototype setups with several applications,
which we built from 1998 to 2002. While running these prototypes we collected experiences from designers, implementers and users and formulated them as guidelines in this paper. All the prototype applications heavily use location information for providing their functionality. We found
that location is not only of use as information for the application but also important for communicating context. In this
paper we introduce the concept of spatial-aware communication where data is communicated based on the relative location of
digital artefacts rather than on their identity.
Correspondence to: Michael Biegl, Telecooperation Office (TecO), University of Karlsruhe, Vincenz-Prieβritz-Str. 1 D-76131 Karlsruhe, Germany.
Email: michael@teco.edu 相似文献
20.
Workflow management systems (WfMS) offer a promising technology for the realization of process-centered application systems.
A deficiency of existing WfMS is their inadequate support for dealing with exceptional deviations from the standard procedure.
In the ADEPT project, therefore, we have developed advanced concepts for workflow modeling and execution, which aim at the
increase of flexibility in WfMS. On the one hand we allow workflow designers to model exceptional execution paths already
at buildtime provided that these deviations are known in advance. On the other hand authorized users may dynamically deviate
from the pre-modeled workflow at runtime as well in order to deal with unforeseen events. In this paper, we focus on forward
and backward jumps needed in this context. We describe sophisticated modeling concepts for capturing deviations in workflow
models already at buildtime, and we show how forward and backward jumps (of different semantics) can be correctly applied
in an ad-hoc manner during runtime as well. We work out basic requirements, facilities, and limitations arising in this context.
Our experiences with applications from different domains have shown that the developed concepts will form a key part of process
flexibility in process-centered information systems.
Received: 6 October 2002 / Accepted: 8 January 2003
Published online: 27 February 2003
This paper is a revised and extended version of [40]. The described work was partially performed in the research project “Scalability
in Adaptive Workflow Management Systems” funded by the Deutsche Forschungsgemeinschaft (DFG). 相似文献