4 Layers in an SOA

There are 4 layers in an SOA:

• Business Processes
• Business Services
• Integration Services
• Enterprise Resources

Enterprise Resources

• existing applications
• COTS systems (consumer, off the shelf)
• Object Oriented systems
• Legacy systems (eg CRM + ERP)
• Data at this layer resides in existing applications and databases
• Operations have a specific, structured interface
• Operations return structured responses
• These applications provide transactions
  • single, logical units of work in the enterprise operational systems
• Responsible for reading, writing and modifying data

Integration Services

• Provide access and interfaces to existing applications
• Expose existing applications as services
• Involve translation from whats actually available in the application to whats desired as an enterprise service

Business Services

• Provide high-level functionality
• Provide an interface abstraction from the implementations in layers below
• Provide virtual implementation of related business processes that can be re-used across multiple systems
• Break the direct dependance between business processes and the underlying applications
• provide business processes (eg customerProfiling) through the logical grouping of related operations (eg search customer by email)

Business Processes

• Series of operations that are executed in an ordered sequence
• Described in a business process model (BPM)
• Executed by a business process management system (BPMS)
• Included in orchestration in terms of
  • Execution
  • Sequencing
  • Selection
• Provide long-running  sets of activities
• Operate on business documents
• Composed of business activities

Sources: https://en.wikipedia.org/wiki/Service-oriented_architecture