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Thomas Erl

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Top Stories by Thomas Erl

Many are comparing notes on two well-publicized paths to achieving SOA. The bottom-up approach is currently the most common variety, where Web services are created on an "as need" basis to fulfill mostly integration-related requirements. These services are typically application specific and simply re-create traditional integration channels over the open Web services communication framework. The top-down approach, on the other hand, is one of analysis, deep thought, and patience. Service-orientation is infused into the business process layer so that services can be modeled in alignment with business models. The models themselves may need to be built or further refined in order to fully incorporate service-orientation principles. Then, of course, there's the middle ground - an approach that tries to balance the requirements of the top-down strategy with the efficiency... (more)

Book Excerpt: Fundamental Cloud Architectures

"This chapter is from the book, 'Cloud Computing: Concepts, Technology & Architecture' authored by Thomas Erl with Zaigham Mahmood and Ricardo Puttini, published by Pearson/Prentice Hall Professional, May 2013, ISBN 0133387526, Copyright 2013 Arcitura Education Inc. For more info please visit: http://www.informit.com/store/cloud-computing-concepts-technology-architecture-9780133387520" This chapter introduces and describes several of the more common foundational cloud architectural models, each exemplifying a common usage and characteristic of contemporary cloud-based environmen... (more)

Introducing SOA Design Patterns

Originally inspired by techniques used to design buildings and cities, and popularized by the Gang of Four during the mainstream emergence of object-orientation, design patterns have seen us through the various shifts in architecture, technology, and, of course, design. Pattern catalogs have periodically emerged, one building on the other, and each revealing a set of problem-solving techniques and providing invaluable insights as to how and when those techniques should be used to help us attain our design goals. SOA has its own history, having risen out of a haze of ambiguity to e... (more)

SOA Pattern of the Week (#2): Non-Agnostic Context

Should a service only be considered a service if it's reusable? The answer to this question, as asserted by this pattern, is a firm "no." While agnostic services (services providing multi-purpose logic with reuse potential, as per the Agnostic Context pattern), receive the most attention during service modeling and design phases, it can often be short-sighted to focus only on agnostic service logic. Non-agnostic logic represents any type of functionality that is unique to a given business process or task. In other words, non-agnostic logic is single-purpose in nature and therefo... (more)

Cloud Computing, SOA and Windows Azure - Part 4

For a complete list of the co-authors and contributors, see the end of the article. The following section demonstrates the creation of a simple "Hello World" service in a Windows Azure hosted application. Note: If you are carrying out the upcoming steps with Visual Studio 2008, you will need to be in an elevated mode (such as Administrator). A convenient way of determining whether the mode setting is correct is to press the F5 key in order to enter debug mode. If you receive an error stating "the development fabric must be run elevated," then you will need to restart Visual Studi... (more)