Oracle SOA Tutorials

Complex Event Processing:

In SOA, CEP is often used, not only for external events, but also to detect patterns in the flow of messages between services. When used in this way, it becomes an extension of message monitoring.

CEP provides the following benefits:

- Simplification of software structure – by removing functionality that is not business-related from the business software services

- Ability to adapt quickly to different external environments – by concentrating in one place the logic that relates environmental events to business events

- Improved manageability and security – when used with performance measurement and security event detection

Service Composition:

Service composition is the putting together of a number of simple services to make a more complex one. For example, a “product sale” web service could be composed of simpler “product selection”, “shopping cart review”, “payment method selection”, “credit card payment”, and “invoice payment” services. Service composition provides a key benefit:

- Ability to develop new function combinations rapidly

For example, if it is decided that the product sale service should cater for a new method of payment – “Internet cash” – this can be done by developing a new “Internet cash payment” service, and including it in the composition.

Service Discovery:

When a program uses a software service, the identity of that service can be explicitly given in the program code. For example, where services are implemented as Java objects, their methods can be invoked by name by user programs. Where messaging is used, the destinations of the messages can be explicitly named at programming time. This is called hard-wiring of service connections.

Hard-wiring is a simple approach, but it has limitations. A different and much more flexible approach is service discovery. In this approach, the identity of the target service is not known at programming time, but is discovered at run time. The user program finds target services that meet its requirements, and chooses one of them.

The benefits of service discovery are:

- Ability to optimize performance, functionality, and cost – by selecting component services by these criteria

- Easier introduction of system upgrades – an upgraded service can be made available for selection in parallel with the one that it replaces, which can then be withdrawn

Asset Wrapping:

An important feature of SOA is the recognition that the assets perform services, and the development of software façades that provide access to these assets and have interfaces that are in the same form as the interfaces to other software services of the enterprise. This is called asset wrapping.

When an enterprise adopts an SOA, asset wrapping is typically applied to existing application software packages. This provides a significant benefit:

- Ability to integrate existing assets – which means that the value of an enterprise’s existing assets is preserved, the cost of developing or acquiring replacements is avoided, and there is a smooth migration path from the old architecture to the new one

Virtualization:

A façade can present to the consumer a virtual asset that does not correspond to the real underlying assets. This technique is called virtualization. Virtualization can be used to enable programs that were written to use one asset to be executed with a different asset. For example, there are so-called “hypervisors” that can provide different operating system environments to programs running on a single CPU. But in the context of SOA it is more commonly used to create virtual assets that are functionally similar to the underlying assets. This can deliver two benefits:

- Improved reliability – through redundant operation of the underlying assets, so that one can take over when another fails or is withdrawn for maintenance

- Ability to scale operations to meet different demand levels – through dynamically increasing or reducing the number of underlying assets that support a real asset, as demand rises and falls

Model-Driven Implementation:

Model-driven implementation refers to the automatic realization of a system or application from an abstract model. Where the model starts at a high level of architectural abstraction, it is usually referred to as Model-Driven Architecture (MDA).

SOA lends itself particularly well to model-driven implementation, because it is based on a high-level software module concept (the service) for which there are good definition and interface standards.

Model-driven implementation provides:

- The ability to develop new functions rapidly – an important form of agility

In SOA, model-driven implementation can be applied to service compositions as well as to software services.

Benefits of SOA:

• Improves developer productivity through easy-to-use, drag-and-drop features for rapidly assembling metadata-driven business applications
• Enables highly flexible and responsive applications through event-driven SOA
• Delivers visibility, flexibility, and speed through best-of-breed tools that provide industry-leading functionality
• Enables organizations to adopt suite components incrementally to suit the needs of specific project