Defining SOA

Service Orientated Architecture (SOA) is currently a popular subject with no consensus or standardized reference model to define it. SOA can be defined as an evolution of the Component Based Architecture, Interface Based Design (Object Based), and Distributed Systems of the 1990s:

• Component Based Architecture- is an architecture where the functionality of the whole is divided into smaller functions, each encapsulated in a component, example: email architecture
• Distributed System- is an extension of components-based architecture and refers to components that may exist in different physical locations
• Reusability and repurposing are often primary business drivers for adopting an SOA

SOA can also be defined as being an architectural paradigm for components of a system and interactions or patterns between them. A component offers a service that waits in a state of readiness. Other components may invoke the service in compliance with a service contract. The following main concepts are consistent in all SOA concepts:

• Services
• Service descriptions
• Advertising and discovery
• Specification of an associated data model
• Service contract

Currently, there is no normative or standards-based consensus on what definitively constitutes SOA, however service concepts work to define behavior in practice. Most architectures that are called SOA include:

• A service provider
• A service consumer
• Some messaging infrastructure

The core business driver for SOA as an integrated technology is its ability to lower integration costs by making it possible to rapidly adapt a system's core functionality to be extended and repurposed to multiple consumers.
IT workers may face many challenges when adapting SOA, including:

• Limited budgets
• Constantly changing technologies
• Business requirements that must be integrated with each other
• Application functionality that must be extended

Service Orientated Architecture (SOA) may be the next evolutionary step in computing environments, based on the use of distributed objects and components.