What is service-oriented architecture(SOA)

The following diagram is an example of a service-oriented architecture using Web services. Click on the yellow boxes below to obtain more information on a subject.

Amidst all the SOA-related activity that is currently underway, there still remains a significant amount of confusion as to what exactly constitutes a service-oriented architecture. Some qualify an SOA project by the fact that Web services technologies are being used, while others classify SOA as a Web-centric variation of object-oriented design. What has become more clear than the actual meaning of SOA is the strategic vision that has emerged around it. This vision is comprised of a set of goals and benefits that most stakeholders fully expect to see realized when they support and commit to SOA initiatives. However, because the "SOA" acronym has been used to brand products, technologies, and even projects without a clear understanding of its meaning, many of these expectations have been and will continue to remain unfulfilled. For example, the common (and dangerous) assumption that a solution is service-oriented solely because it uses Web services has led to much disappointment. There is, in fact, a wealth of information out there that communicates the meaning of SOA in detail. The only problem is that this information is fragmented - distributed across marketing literature, technology specifications, media reports, and independent research efforts. While there is no one recognized definition of SOA, there is a baseline of concepts and principles that exists among all of the organizations, platforms, and initiatives that have influenced and continue to shape the SOA movement. For any IT professional, project team, or organization interested in moving ahead with SOA, this baseline perspective is extremely important to understand because it reflects a current, industry-level, and vendor-agnostic representation of what SOA is in the real world. My third book in the Prentice Hall Service-Oriented Computing Series from Thomas Erl (entitled SOA: Principles of Service Design) is dedicated to exploring the service-orientation design paradigm and service design techniques. It begins with some introductory chapters that leverage years of on-going industry research as part of my involvement in projects for SOA Systems Inc. This research has been synthesized to establish the aforementioned baseline perspective of SOA, and to further broaden the discussion to encompass the service-orientation design paradigm and service-oriented computing as a whole. The book manuscript (including the content on this site) was subjected to a rigorous technical review involving over 60 reviewers from different vendors, organizations, and professions across North America, Europe, and Asia. The book ended up being formally endorsed by members of major SOA vendors, including IBM, Microsoft, Oracle, BEA, Sun, SAP, HP, and Intel. With permission from Prentice Hall, I was able to publish some of the book’s introductory content on a modest network of Web sites (in exchange for posting book cover images on Web page footers). The primary reason these sites exist is to provide convenient on-line reference content for readers of the book series. It also helps us avoid publishing redundant content in the books, so that each title remains focused on its specialized subject matter. WhatIsSOA.com essentially acts as the starting point for these sites by establishing some fundamental terminology and providing specific coverage of the strategic goals and benefits that collectively represent the modern-day vision of SOA and service-oriented computing. The last set of pages provide further supplementary content that addresses implementation technologies, processes, and other deliverables that are common in real world SOA projects. Although this site positions SOA within the service-oriented computing platform, it only hints at what it means for solution logic to be considered "service-oriented." That particular topic deserves a study of its own, which is why I publishedwww.SOAPrinciples.com, a separate Web site dedicated to an exploration of service-orientation.