Types Of Integration
Data Level Integration
Moving data between applications like database, adapter, XML

Application Level Integration
On top of existing application - Using API, components can be build and exposed as a service in the ESB

Business Process Integration
On top of existing application - services are builded and orchestrated

Presentation Integration
Portal or User view integration with Middle tier or Business Process

Web Services
Web services are the latest distributed technology, component over the wire.They provide the technical foundation for achieving interoperability between applications using different software platforms, operating systems and programming languages,Enables any application to be accessed via XML-based calls,XML format is very flexible, allows consumers and providers to be loosely coupled

SOA Application Attributes
Application has a well defined and separated functionality layer
Functional layer has well defined functional entry points (façade)
Entry points are coarse-granined functions
Well defined data interchanges (XML)
Powerful and flexible business process modeling environment

Pros and Cons of Service Oriented Architecture
Benefits of SOA
The Key benefits for implementing the Service Oriented architectures are Adaptable to changing business needs (Agile), Quickly develop or integration and deliver Faster time to market , Business and Process Driven leads to provide new business opportunities, Leverage existing IT assets and increase ROI.

Disadvantage of SOA
Service oriented architecture composed of services efficient to fit for large enterprises, distributed environment. It's not recommended to implement in small - medium sized or in non distributed environment.

About Author / Additional Info:
Arivuvel Ramu
Technical Architect (SOA)
galaxE Solutions, Bangalore, India