Sommerville-Software-Engineering-10ed

Chapter 17.4 ■ Further Reading reading 517
Key Points
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The benefits of distributed systems are that they can be scaled to cope with increasing demand,
can continue to provide user services (even if some parts of the system fail), and they enable
resources to be shared.
Issues to be considered in the design of distributed systems include transparency, openness,
scalability, security, quality of service, and failure management.
Client–server systems are distributed systems in which the system is structured into layers, with
the presentation layer implemented on a client computer. Servers provide data management,
application, and database services.
Client–server systems may have several tiers, with different layers of the system distributed to
different computers.
Architectural patterns for distributed systems include master–slave architectures, two-tier and multitier
client–server architectures, distributed component architectures, and peer-to-peer architectures.
Distributed component systems require middleware to handle component communications and to
allow objects to be added to and removed from the system.
Peer-to-peer architectures are decentralized architectures in which there are no distinguished clients
and servers. Computations can be distributed over many systems in different organizations.
Software as a service is a way of deploying applications as thin client–server systems, where the
client is a web browser.
Further Reading
Peer-to-Peer: Harnessing the Power of Disruptive Technologies. Although this book does not have a
lot of information on p2p architectures, it is an excellent introduction to p2p computing and
discusses the organization and approach used in a number of p2p systems. (A. Oram (ed.), O’Reilly
and Associates Inc., 2001).
“Turning Software into a Service.” A good overview paper that discusses the principles of serviceoriented
computing. Unlike many papers on this topic, it does not conceal these principles behind a
discussion of the standards involved. (M. Turner, D. Budgen, and P. Brereton, IEEE Computer, 36 (10),
October 2003) http://dx.doi.org/10.1109/MC.2003.1236470
Distributed Systems, 5th ed. A comprehensive textbook that discusses all aspects of distributed systems
design and implementation. It includes coverage of peer-to-peer systems and mobile systems.
(G. Coulouris, J. Dollimore, T. Kindberg, and G. Blair. Addison-Wesley, 2011).
Engineering Software as a Service: An Agile Approach Using Cloud Computing. This book accompanies
the authors’ online course on the topic. A good practical book that is aimed at people new to this type
of development. (A. Fox and D. Patterson, Strawberry Canyon LLC, 2014) http://www. saasbook.info