Service-Oriented Architecture (SOA) provides for a set of resources that are linked together on demand. This demand access can be from other systems, and/or users, or even applications that link together resources via a set of standards. Lotus Notes 8.5 is built on IBM's release of the Eclipse Rich Client Platform (RCP). Since Lotus Notes 8.5 was built based on a set of standard components, it was a part of a service-oriented architecture. This provides a more extensible server-managed client.
In this chapter, we will introduce the concept of service-oriented architecture and how Lotus Notes 8.5 fits into one. We will explain what an SOA is, its value, and its characteristics. You will also learn how Lotus Notes 8.5 has many characteristics of SOA components, and how it can help you assemble applications that can play a role in an SOA.
Although the concept of an SOA is simple, the components that make up one can be complex. Additionally, the value and perception of an SOA varies with the perspective and role of organizations and people considering one. So in this chapter, we'll start with the basic definition of an SOA and then examine specific aspects of SOAs.
The definition of SOA can often be taken further by adding the word "business", since the inherent value comes from business orientation and enablement.
In computing, the term SOA expresses a software architectural concept that defines the use of services to support the requirements of software users. In an SOA environment, nodes on a network make resources available to other participants in the network as independent services they access in a standardized way. Most definitions of an SOA identify the use of web services (using SOAP and WSDL) in its implementation. However, you can implement SOA using any service-based technology.
SOAs can be used to:
- Build distributed systems that deliver application functionality as services to either end-user applications or other users
- Design and implement distributed systems that allow a tight correlation between the business model and its IT implementation
- Manage services made available by different software packages for reuse and reconfiguration
These uses of SOA highlight the fact that they encompass a wide range of interests.
There are many ways to implement and view an SOA. The specific approach and value proposition depends on the needs of the business and the role of the organization or person considering the SOA. In this chapter, we will focus on how businesses can reuse existing Notes-based functions, and how to take existing Eclipse and WebSphere Portal services and incorporate them into new Notes functions.
There are some commonly understood characteristics of an SOA. These include the following:
- Services are reusable and called by many applications
- Service access is with communication protocols rather than direct calls
- Services are loosely coupled so that they are autonomous
- Interfaces are defined in a platform-independent manner
- Services are encapsulated so that the interface doesn't reveal how the service was implemented (this is called abstraction)
- Services share a formal contract
- Services are composable (able to be assembled into composite applications)
- Services are stateless
- Services are discoverable
Later in this chapter, we will examine some of these characteristics and see how Lotus Notes 8.5 can interact with an SOA.
From a business perspective, SOA is about identifying, surfacing, and integrating business services to meet business needs.
From an IT perspective, SOA is about responding quickly to changing business needs. IT organizations must determine what style, patterns, or principles provide architecture capable of responding in a timely fashion. These questions must be answered with the understanding that existing applications and systems have been built over time and are hardwired together.