Bartlang Architecture and Methods for Flexible Content Management in Peer-to-Peer Systems

2010
ISBN: 978-3-8348-9645-2
Verlag: Vieweg & Teubner
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 240 Seiten, eBook

At times when the IT manager's best friend is systems consolidation (which is a euphemism for centralisation), it may come somewhat as a surprise for you that this book investigates decentralisation in the context of content management systems. It may seem quite obvious that content will and should be managed by the party who creates and owns the content, and hence should be held in a-somewhat-centralised and managed location. However, over the past few years, we have been witnesses of some important trends and developments which call for novel ways of thinking about content management and maybe even broader, about computer systems in general. First, ongoing business globalization creates natural distribution of information at a corp- ate level, as well as decentralization of control over business resources and business processes. Changing alliances with partners require ?exible architectures for content management that canadapttochangingconstellations, roles, andaccessrights. Second, theneedforoutsourcing and resource e?ciency has brought about concepts of virtualization, recently culminating in the cloud computing buzzword. Virtualization of content management services requires - tremely scalable and ?exible underlying information and communication architectures. These kinds of solutions are theoretically and practically impossible to implement based on c- tralised client-server architectures. Third, we are currently experiencing a dramatic shift in the roles of consumers in the Internet. The times have gone when quality content was only delivered by publishers and news agencies. Wikis and other Web 2. 0 tools empower consumers to produce and publish their personal content.

Dr. Udo Bartlang completed his doctoral thesis at the Faculty of Mathematics/Computer Science and Mechanical Engineering (Department of Informatics, Business Information Technology Unit), Clausthal University of Technology. The thesis was conducted at Siemens Corporate Technology, Munich.

Zielgruppe

Research

Autoren/Hrsg.

Bartlang, Udo

Inhaltsverzeichnis

1;Foreword;6
2;Danksagung;8
3;Abstract;9
4;Zusammenfassung;11
5;Contents;13
6;List of Figures;17
7;List of Tables;19
8;1 Introduction;20
8.1;1.1 Sample Scenarios of a Peer–to–Peer-Based Content Repository;22
8.1.1;1.1.1 Cross-Enterprise Business Collaboration;22
8.1.2;1.1.2 Intra-Enterprise Knowledge Management;25
8.2;1.2 Problem Statement and Research Challenges;29
8.2.1;1.2.1 Research Challenges Regarding the Content Model;30
8.2.2;1.2.2 Research Challenges Regarding the Content Repository Model;30
8.2.3;1.2.3 Research Challenges Regarding the Peer–to–Peer Model;32
8.3;1.3 Main Research Contributions of this Thesis;33
8.4;1.4 Publications;35
8.5;1.5 Outline;36
9;2 Background;38
9.1;2.1 Content Repositories;39
9.1.1;2.1.1 Content versus Data;41
9.1.2;2.1.2 Content Management;42
9.1.3;2.1.3 Content Management Systems;42
9.2;2.2 Distributed Systems, Algorithms, and Methods;44
9.2.1;2.2.1 Node Model;45
9.2.2;2.2.2 Communication Models;45
9.2.3;2.2.3 Failure Models;47
9.2.4;2.2.4 Consensus Algorithms;48
9.2.5;2.2.5 Fault-Tolerant State Machines;50
9.2.6;2.2.6 Group Communication;51
9.2.7;2.2.7 Dynamic Code Loading;51
9.3;2.3 Peer–to–Peer Systems;52
9.3.1;2.3.1 Centralised Peer–to–Peer Overlays;53
9.3.2;2.3.2 Unstructured Peer–to–Peer Overlays;54
9.3.3;2.3.3 Structured Peer–to–Peer Overlays;55
9.4;2.4 Distributed File Systems;56
9.4.1;2.4.1 Client–Server-Based Systems;57
9.4.2;2.4.2 Peer–to–Peer-Based Systems;59
9.5;2.5 Distributed Database Systems;61
9.5.1;2.5.1 Client–Server-Based Systems;62
9.5.2;2.5.2 Peer–to–Peer-Based Systems;64
9.6;2.6 Summary;65
10;3 Analysis of Content Repository Requirements in a Peer–to–Peer Case;67
10.1;3.1 Methodology of Analysis;67
10.2;3.2 Definition of Functional Building Blocks Using the Content Repository API for Java Technology;68
10.2.1;3.2.1 Content Repository Model;69
10.2.2;3.2.2 Content Repository Functions;71
10.2.3;3.2.3 Operational Scope;79
10.3;3.3 Dependence Relationships between Functional Building Blocks;80
10.3.1;3.3.1 Service Functionality Dependence;80
10.3.2;3.3.2 Influence Dependence;82
10.4;3.4 Suitability of Peer–to–Peer Overlays for Content Repository Functionality;83
10.4.1;3.4.1 Functional Content Repository Requirements for a Peer–to–Peer Approach;84
10.4.2;3.4.2 Non-Functional Content Repository Requirements for a Peer–to–Peer Approach;84
10.5;3.5 Summary;86
11;4 Design of a Generic Peer–to–Peer Content Repository System Architecture;88
11.1;4.1 Architectural Model;89
11.1.1;4.1.1 Logical View;89
11.1.2;4.1.2 Process View;89
11.1.3;4.1.3 Development View;90
11.1.4;4.1.4 Physical View;90
11.1.5;4.1.5 Scenarios;90
11.2;4.2 Generic Content Repository Architecture;91
11.2.1;4.2.1 Modular Decomposition;91
11.2.2;4.2.2 Persistent Storage Management;94
11.3;4.3 Generic Content Mapping;97
11.3.1;4.3.1 Item Naming Concept;97
11.3.2;4.3.2 Flexible Content Item Policies;100
11.4;4.4 Generic Peer Architecture;101
11.4.1;4.4.1 Internal Peer Structure;101
11.4.2;4.4.2 Dynamic Service Integration;104
11.5;4.5 Related Work;106
11.6;4.6 Summary;108
12;5 Methods for Flexible Content Repository Functions in Structured Peer–to–Peer Overlays;109
12.1;5.1 DhtFlex: A Distributed Algorithm for Flexible Atomic Data Management;109
12.2;5.2 System Context of DhtFlex;111
12.2.1;5.2.1 System Model;111
12.2.2;5.2.2 System Architecture;112
12.2.3;5.2.3 System Interface;116
12.3;5.3 Functionality of DhtFlex;116
12.3.1;5.3.1 Annotated Data Resources;117
12.3.2;5.3.2 Recast Case;117
12.3.3;5.3.3 Put Case;123
12.3.4;5.3.4 Get Case;125
12.3.5;5.3.5 Overlay Breakup Detection;127
12.4;5.4 Flexible Content Repository Functions;128
12.4.1;5.4.1 Content Mapping;128
12.4.2;5.4.2 Persistent Content Storage;130
12.5;5.5 Related Work;133
12.6;5.6 Summary;135
13;6 Methods for Flexible Content Repository Functions in Hybrid Peer–to–Peer Overlays;136
13.1;6.1 Reconfigurable Peer–to–Peer Service Groups;137
13.2;6.2 System Context of Peer–to–Peer Service Groups;139
13.2.1;6.2.1 System Model;139
13.2.2;6.2.2 System Architecture;140
13.2.3;6.2.3 System Interface;144
13.3;6.3 Functions of Peer–to–Peer Service Groups;145
13.3.1;6.3.1 Lifecycle Management;145
13.3.2;6.3.2 Decentralised Dynamic Code Loading of Service Functions;149
13.3.3;6.3.3 Consensus-Based Peer–to–Peer Group Communication;154
13.4;6.4 Flexible Content Repository Functions;163
13.4.1;6.4.1 Content Mapping;163
13.4.2;6.4.2 Persistent Content Storage;165
13.5;6.5 Related Work;168
13.6;6.6 Summary;171
14;7 Evaluation;173
14.1;7.1 Methodology;173
14.1.1;7.1.1 Architecture Evaluation;173
14.1.2;7.1.2 Method Evaluation;175
14.2;7.2 Peer–to–Peer Content Repository System Architecture;176
14.2.1;7.2.1 Architectural Styles;176
14.2.2;7.2.2 Quality Attributes;177
14.2.3;7.2.3 Scenarios;179
14.3;7.3 Methods for Flexible Content Repository Functions in Structured Peer–to–Peer Overlays;181
14.3.1;7.3.1 Reliability;181
14.3.2;7.3.2 Consistency;183
14.3.3;7.3.3 Reconfigurability;192
14.3.4;7.3.4 Scalability;192
14.3.5;7.3.5 Performance;196
14.4;7.4 Methods for Flexible Content Repository Functions in Hybrid Peer–to–Peer Overlays;201
14.4.1;7.4.1 Reliability;201
14.4.2;7.4.2 Consistency;202
14.4.3;7.4.3 Reconfigurability;203
14.4.4;7.4.4 Scalability;203
14.4.5;7.4.5 Performance;204
14.5;7.5 Summary;208
15;8 Conclusion and Outlook;210
15.1;8.1 Conclusion;210
15.2;8.2 Future Work;213
16;Bibliography;217

Background.- Analysis of Content Repository Requirements in a Peer–to–Peer Case.- Design of a Generic Peer–to–Peer Content Repository System Architecture.- Methods for Flexible Content Repository Functions in Structured Peer–to–Peer Overlays.- Methods for Flexible Content Repository Functions in Hybrid Peer–to–Peer Overlays.- Evaluation.- Conclusion and Outlook.

Leseproben

4 Design of a Generic Peer–to–Peer Content Repository System Architecture (S. 71-72)

The architecture of a software system may be regarded as its essential description to understand it. For instance, such understanding refers to the role of the major system components and, in particular, their coupling. A “software architecture shall de?ne a simple model of major components and their interactions, it may act as reusable, transferable abstraction of a software system” [55].

An architecture acts as a method to organize and structure a system. An important aim is to reduce the overall complexity to illustrate such system promoting the principles of decomposition and transparency, for example, as functionality is encapsulated within certain system parts, the details should be hidden, turning the focus rather on each part’s characteristics. Hence, architectural design has major impact on a system’s functionality, as it de?nes the degree of modularity a?ecting maintenance and reliability.

In this chapter, the architecture illustrates the responsibilities each system part has and how these parts interact to ful?l functional and non-functional requirements of peer–to–peer (P2P) based content repository functions, as presented in Chapter 3. One key to meet the imposed requirements is ?exibility. This motivates a generic architecture, which is suitable for di?erent communication and storage paradigms. Thereby, the term generality refers to “the degree to which a system or component performs a broad range of functions” [176]: accordingly, the generic architecture needs to support, for example, the introduced concepts of sessions and workspaces, and to integrate di?erent storage back-ends, the latter may comprise the integration of local systems, distributed client–server systems, or decentralised (structured or hybrid) P2P systems.

This chapter is structured as follows: Section 4.1 introduces the applied methodology to present the P2P-based content repository architecture. Then, Section 4.2 describes the generic architecture for the overall content repository system. It introduces a layer model to decompose the system into several parts of responsibility, and illustrates the management to cope with persistent storage. Next, Section 4.3 introduces a method for generic content mapping, which supports transparency at di?erent levels. It explains a concept to bundle items and introduces ?exible content data policies. Subsequently, Section 4.4 shows a generic peer architecture explaining a peer’s basic services and introducing a method to dynamically integrate additional peer services. Section 4.5 discusses related work.

Finally, Section 4.6 concludes and summarises this chapter. 4.1 Architectural Model Overall, a software architecture deals with the design and implementation of a software’s highlevel structure [108]: it is basically the result of composing an amount of architectural elements in some well-determined way to satisfy the major functional and non-functional requirements of the system. The methodology to present the P2P-based content repository architecture is oriented on the “4+1” view model of software architectures [108]: the organisation of the architecture’s description uses multiple, concurrent views—each one addressing a speci?c set of concerns. This allows to cope separately with the functional and non-functional imposed requirements— as introduced in Chapter 1.1 Figure 4.1 [108] illustrates the ?ve main views.

Über Autor(innen)

Dr. Udo Bartlang completed his doctoral thesis at the Faculty of Mathematics/Computer Science and Mechanical Engineering (Department of Informatics, Business Information Technology Unit), Clausthal University of Technology. The thesis was conducted at Siemens Corporate Technology, Munich.