There is no doubt that businesses have benefited from information technologies and have moved into the so-called digital age. Still, there are some commonly prevailing complaints: "IT is too complex", "IT is too expensive", and "IT is too slow". The main reason for increased attention to SOA these days is the expectation that by exposing and leveraging the existing IT assets as services, SOA will help simplify IT applications development and operations, and will help businesses gain significant cost advantages and agility. Interestingly, SOA is not the first time that the industry tried to enhance the business benefit of IT.

Elements of the SOA paradigm have been in the making for nearly three decades. The present day service-oriented computing has its roots in computing models like modular programming, client-server computing, object-oriented programming, component-based and model-based developments, and in distributed computing technologies like Distributed Computing Environment with remote procedure calls and Distributed File Systems (DCE/RPC/DFS), Message-Oriented Middleware (MOM), Object Request Brokers (ORBs). Contemporary SOA also leverages tremendous advancements of the last decade in LAN- and WAN-based computing and in the Internet technologies.

Unlike many of the technologies of the past, modern SOA utilizes technology and vendor neutral standards like XML, HTTP, and Web Services (WS-*) that are heavily backed by all leading software vendors. This has now led to a much stronger acceptance of SOA as compared to similar technologies and styles that preceded it. With the introduction of Enterprise Service Bus (ESB) products, it has become much easier to mediate service requests and to build shared services infrastructure layers on top of IT assets. These service infrastructure layers can effectively support higher-level composite applications like business processes and portals while insulating them from changes below the service layer, and thus facilitating application rationalization and legacy modernization.

With essential philosophies and practices demystified, SOA is now becoming the foundation of many mission-critical applications—this drastically increases the performance, scalability, reliability, and policy enforcement requirements of SOA solutions. Services layers are often the building blocks on which agile business processes rest. Many real-life applications require handling of events and it is becoming important for SOA-enabling infrastructures to be able to accommodate event handling and processing alongside services. Services are also being seen as key ingredients in shared computing environments such Software-as-a-Service (SaaS) or cloud computing. Does this level of industry acceptance of SOA mean that we have attained SOA nirvana? The answer, of course, is No, or at least, Not Yet! Part of the reason is the increase in complexity as the SOA solutions are aimed at non-trivial and mission-critical applications. The complexity, at least as it relates to implementation of the solutions, mainly arises from the fact that to build such applications, you not only have to access and orchestrate services, but also, as in tiered compositions, orchestrate the orchestration of services, or include human workflow features like approvals and manual exception handling, or use business rules to add flexible decision making. In such cases, multiple development environments with corresponding technologies, metadata, and runtime engines would be necessary.

The developers would have to deal with these different development environments and would have to integrate the individual components themselves. The operations people would have to deal with the nuances of such custom integration of integration components for deployment, monitoring, and management. This complexity eats into the potential SOA benefits by significantly increasing the activity costs for SOA solutions.

Therefore, what is needed is a service platform where the design-time elements of all the necessary tools are available in one Integrated Development Environment (IDE), where such complex solutions can be composed easily out of the necessary components with drag-and-drop type simplicity, and from where the composed solution can be deployed and managed as one unit. From a technical perspective, emergence of such service platforms is the key to the next generation of SOA-enabling infrastructures. Of course, some guiding disciplines would be required to create such a platform. The recently proposed technology and vendor neutral Service Component Architecture (SCA) specification, that is backed by most of the leading software vendors concerned with SOA, is an important step in that direction. As we will see throughout this book, Oracle SOA Suite 11g leverages SCA in order to deliver such a service platform.